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Biomedical subjects

D Morton

Publications and source records attributed to D Morton.

At least 91 records · Page 5Linked to original sources
PubMed1980

Distribution of iron in the gastrointestinal tract of the common vampire bat: evidence for macrophage-linked iron clearance.

Iron in the tissues of the digestive tract of the common vampire bat (Desmodus rotundus) has been studied using histochemical, electron microscopic, and autoradiographic methods. This animal is an obligate sanguivore and has a daily intake of dietary iron 800 times that of man. The amount and distribution of tissue iron is not affected by either a single blood meal or starvation but does reflect the degree of siderosis of each animal's liver and spleen. By 7 days after the injection of a trace amount of 55Fe into the peritoneal cavity, labelled siderotic macrophages are present both on the serosa and within the walls of the stomach and intestine. In the lower intestine, such cells can be derived from the germinal centers of Peyer's patches. Siderotic macrophages are often situated in the lamina propria under areas of siderotic epithelium. Label is also present in the apical cytoplasm of mucosal epithelial cells, a region of abundant siderosomes. The ultrastructure of these organelles is extremely variable. Accumulations of membranous whorls and stacks, "stippled bodies," ferritin molecules, and larger "ferruginous" complexes are bounded by one or a number of membranes. Iron is excreted when these epithelial cells are desquamated into the gut lumen. Similar Prussian blue-positive granules are present in the feces. Unlike other glandular cells, the parietal cells of the fundic caecum are siderotic. Their cytoplasm contains abundant siderosomes and ferritin with accumulations of amembranous ferritin bodies in the intracellular canalicular spaces. Prussian blue-positive granules are present in the lumens of fundic glands.

Animals↗
PubMed1980

5' flanking sequence signals are required for activity of silkworm alanine tRNA genes in homologous in vitro transcription systems.

We have used homologous in vitro transcription to examine the nucleotide sequences required for activity of cloned Bombyx mori tRNA2Ala genes. We have compared the transcriptional properties of an intact gene and a truncated derivative of the same gene lacking all but 11 nucleotides of normal 5' flanking DNA, and we find that at least two regions of DNA are required for accurate transcription of tRNA2Ala genes by homologous B. mori extracts. One of these sites is retained in the truncated gene and may be within the tRNA coding sequence. Competition experiments with intact and truncated genes indicate that this site probably acts by binding a factor necessary for specificity in polymerase III-catalyzed transcription. The second required site is removed by the Hind III cleavage used to produce shortened genes and thus must be 11 nucleotides or more upstream from the transcription initiation point. Possible roles for this site are discussed.

Alanine↗
PubMed1980

Exocrine pancreatic secretion in rats treated with reserpine after stimulation with pilocarpine, dopamine, and caerulein.

Pancreatic juice was collected in vivo from control and reserpine-treated rats after stimulation with pilocarpine (0.2 mg/100 g body weight), dopamine (6--7 mg/100 g body weight), caerulein (90--100 pmole total dose) or with a combination of caerulein and secretin (6 u/100 g body weight) and the volume, amylase, bicarbonate and chloride outputs were compared. The results indicate that the secretory response to the three secretagogues was significantly reduced in the drug treated animals. Thus, the volumes of pancreatic juice were 57.0, 60.5, and 15.7% of those obtained in control rats after stimulation with, respectively, pilocarpine, dopamine, and caerulein. Amylase output was 63.8, 67.1, and 21.0% and bicarbonate output was 29.9, 46.8, and 6.2% of those observed in untreated rats after the same stimulants. Fluid secretion increased in the treated animals to 71.3% of that of controls when both caerulein and secretin were administered together and amylase output became greater than in control rats (151%). However, bicarbonate output was still 55.2% of that of controls with this combined stimulation. It is concluded that chronic reserpine administration impairs exocrine pancreatic secretion and that this effect involves both the acinar and ductal portions of the gland. This impairment involves the physiologic responses of these two segments of the glandular epithelium to both neural and hormonal stimulants. These findings suggest that the exocrine pancreatic disturbance in reserpine-treated rats may be similar to that observed in cystic fibrosis (CF), and because the treated rat has been proposed as a model for the human disease, they suggest the use of this model as a test system for the study of the pancreatic secretory abnormality in CF.

Amylases↗
PubMed1980

HBe-Antigen in the course and prognosis of hepatitis B infection: a prospective study.

The prognostic significance of the HBe-antigen (HBeAg) in the course and outcome of type B hepatitis was studied prospectively in 71 susceptible oncology patients. The patients had been exposed to tumor cell vaccines inadvertently contaminated with hepatitis B surface antigen (HBsAg)-containing plasma. Forty-five patients (63%) were infected. These 45 showed three types of acute seroresponse: HBsAg and HBeAg, 28 patients (62%); HBsAg alone, 8 patients (18%); and a primary antibody to HBsAg (anti-HBs) response, 9 patients (20%). There was no significant difference in acute course and outcome between the two HBs-antigenemic groups. All primary anti-HBs responders had asymptomatic infections. Seventeen patients receiving chemotherapy during the period of hepatitis B exposure were significantly more prone to symptomatic infection with acute HBs-antigenemia, and 2 of these patients developed chronic active hepatitis. The HBeAg is common early in acute hepatitis B among solid tumor patients and at this stage in disease has no prognostic significance independent of HBsAg.

Adult↗
PubMed1978

Preduodenal portal vein: Two cases with differing presentation.

Preduodenal or precholedochal veins are rare developmental anomalies of considerable surgical importance. Injury to these structures because of failure to recognize them during operations for unrelated diseases may result in thrombosis or hemorrhage. We recently encountered this anomaly twice, once in a newborn infant with duodenal obstruction and once in a 54-year-old woman undergoing cholecystectomy. The preduodenal vein was not the primary cause of obstruction in the infant, but injury to the previously unrecognized percholedochal vein in the woman resulted in a considerable loss of blood. Besides describing and illustrating these two cases, we also discuss the anatomy and the embryology of these structures and briefly review the patterns of 44 previously reported cases that we found.

Arteriovenous Malformations↗
PubMed1978

Synthesis of T4 DNA and bacteriophage in the absence of dCMP hydroxymethylase.

Several lines of research have suggested that the dCMP hydroxymethylase (HMase) coded by bacteriophage T4 is an essential protein in a DNA replication complex, as well as a supplier of hydroxymethyl dCMP for phage DNA synthesis. We show that a mutant [HMase, dCTPase, endonuclease II, endonuclease IV] which lacked this enzyme made cytosine-containing DNA at about two-thirds of the normal rate. When coupled with an alc mutation which permitted synthesis of late proteins, a small burst of phage was produced whose DNA contained no hydroxymethylcytosine. This pentuple mutant made both early and late proteins with abnormal kinetics, whereas the HMase+ parent showed normal kinetics. However, intracellular phage DNA showed no gross abnormalities in alkaline sucrose gradients. We conclude that HMase is not required for DNA synthesis when hydroxymethyl dCMP is not needed as a substrate; however, its absence still impairs both replication and transcription.

Coliphages↗
PubMed1978

A comparison of iron histochemical methods for use on glycol methacrylate embedded tissues.

Four histochemical tests for iron and four procedures for its removal were investigated in regard to their suitability for glycol methacrylate embedded tissues. The HCl-ferrocyanide and chlorate hematoxylin methods were easily modified for plastic sections. The latter does not use iron-containing reagents. Desiderization was complete both after a fifteen minute exposure in 1% Na2S2O4 in 0.1 M acetate-HCl buffer (pH 4.5) and, if an acid method is preferred, after twelve hours in 5% oxalic acid. A six hour treatment in 3.7 N H2SO4 also removed all histochemical iron but was accompanied by a relatively greater loss of tissue basophilia.

Animals↗
PubMed1977

Repair of pectus excavatum in children under 3 years of age: a twelve-year experience.

From 1964 to 1975, 50 children under 36 months of age had operative repair of severely deforming pectus excavatum. No child died or suffered a serious complication from the operation. Most young children needing early repair of progressive pectus excavatum can be identified by 18 months of age. Forty-five patients in this series (90%) have had a totally satisfactory cosmetic and anatomical result on one- to twelve-year follow-up. Early repair of marked pectus excavatum in young children is safe and is efficacious in providing a suitable body contour.

Age Factors↗
PubMed1970

Immunological factors which influence response to immunotherapy in malignant melanoma.

Antimelanoma antibodies previously demonstrated in the serum of melanoma patients by immunofluorescence have now been detected by a sensitive and quantitative complement fixation technique. The melanoma-specific antibodies detected by both of these techniques show a remarkable correlation with the stage of disease. Study of serums from 63 melanoma patients showed that both the incidence and titer of antibodies to the tumor antigens of malignant melanoma were found to be higher in patients with localized melanoma than in those with widespread metastatic disease. Furthermore, study of serial serum specimens on melanoma patients revealed a drop in antibody titer to undetectable levels with advancing metastatic disease. Additional evidence for the importance of immunological factors in this disease came from studies of delayed cutaneous hypersensitivity in melanoma patients. All patients with localized melanoma were capable of being sensitized to DNCB, whereas all patients who could not manifest delayed cutaneous hypersensitivity to this chemical had widespread metastatic disease. Eight melanoma patients were treated with immunotherapy using BCG as an immunological adjuvant. This therapy produced a rising titer of antimelanoma antibody and temporary tumor regression in five patients. However, only one of these patients has had a complete regression and remains free of disease at two years following treatment. There was a good correlation between the patient's immunological competence and his response to immunotherapy. All patients who could be sensitized to DNCB or tuberculin and developed a fourfold rise in antibody titer had some response to immunotherapy, whereas anergic patients failed to respond to this therapy. These studies indicate that the host immune response to malignant melanoma is an important factor in controlling the progression of this disease. Therefore, immunotherapy may become a useful adjunct to the primary surgical therapy of malignant melanoma.

Antibodies, Neoplasm↗
PubMedDate not supplied

A good practice guide to the administration of substances and removal of blood, including routes and volumes.

This article is the result of an initiative between the European Federation of Pharmaceutical Industries Associations (EFPIA) and the European Centre for the Validation of Alternative Methods (ECVAM). Its objectives are to provide the researcher in the safety evaluation laboratory with an up-to-date, easy-to-use set of data sheets to aid in the study design process whilst at the same time affording maximum welfare considerations to the experimental animals. Although this article is targeted at researchers in the European Pharmaceutical Industry, it is considered that the principles underpinning the data sets and refinement proposals are equally applicable to all those who use these techniques on animals in their research, whether in research institutes, universities or other sectors of industry. The implications of this article may lead to discussion with regulators, such as those responsible for pharmacopoeial testing. There are numerous publications dealing with the administration of test substances and the removal of blood samples, and many laboratories also have their own "in-house" guidelines that have been developed by custom and practice over many years. Within European Union Directive 86/609EEC1 we have an obligation to refine experiments to cause the minimum amount of stress. We hope that this article will provide background data useful to those responsible for protocol design and review. This guide is based on peer-reviewed publications whenever possible, but where this is not possible we have used "in-house" data and the experience of those on the working party (as well as helpful comments submitted by the industry) for a final opinion. The guide also addresses the continuing need to refine the techniques associated with the administration of substances and the withdrawal of blood, and suggests ways of doing so. Data-sharing between laboratories should be encouraged to avoid duplication of animal work, as well as sharing practical skills concerning animal welfare and scientific problems caused by "overdosing" in some way or another. The recommendations in this guide refer to the "normal" animal, and special consideration is needed, for instance, during pregnancy and lactation. Interpretation of studies may be confounded when large volumes are administered or excessive sampling employed, particularly if anaesthetics are used.

Animals↗