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Biomedical subjects

A Lumsden

Publications and source records attributed to A Lumsden.

115 records · Page 7Linked to original sources
PubMed1986

Unusual polypoidal tumours of the nasal cavity: a clinicopathological review of 18 cases.

A variety of nasal conditions may present as simple polypi. Clinically, these lesions, some very rare, present a diagnostic problem. Eighteen cases of unusual lesions which were thought to be simple polyps on clinical grounds are reviewed with the relevant literature. The series includes 2 olfactory neuroblastomas, a haemangiopericytoma and a basal encephalocoele. Atypical features from the history and examination are highlighted. It is emphasized that every nasal polyp must be submitted for histological examination and the pathology report consulted when the patient is reviewed. Failure to do so delays appropriate treatment.

Adolescent↗
PubMed1986

Variceal bleeding.

Explore the source record for details and available documents.

Colitis, Ulcerative↗
PubMed1984

Relation of target encounter and neuronal death to nerve growth factor responsiveness in the developing mouse trigeminal ganglion.

An aim of this study was to define precisely the period in the developmental history of primary sensory neurons during which nerve growth factor (NGF) exerts its growth-promoting effect. The mouse trigeminal ganglion and its peripheral projection were studied at closely staged intervals throughout development using light and electron microscopy, and the influence of NGF and anti-NGF antiserum on neurite outgrowth from ganglion explants was investigated at corresponding stages in culture. By embryonic day 9.5 (E9.5) peripheral fibers were first visible and increased in number until E13. Throughout this period in vitro neurites grew in the presence of anti-NGF. Peripheral fibers initially contacted the epithelium of the mandibular process by E10.5 and the maxillary process by E11. This coincided with the stage in vitro during which the magnitude of neurite outgrowth was significantly increased by NGF. The development of this response was independent of target encounter since it occurred in neurons which had not contacted their targets prior to explantation. There was an approximate one-to-one relationship between the number of neurons in the ganglion and peripheral fibers throughout development. A peak of some 44,400 fibers and 42,600 neurons was reached by E13 and fell to 20,800 and 19,000, respectively, by birth. Neurite outgrowth was elicited by NGF throughout the period of neuronal death. It is argued that the time course of the influence of NGF is consistent with a role as a selective maintenance factor but not as an agent directing initial outgrowth.

Aging↗
PubMed1982

Intra-epithelial mast cells in human airway epithelium: evidence for smoking-induced changes in their frequency.

A morphological and quantitative study was performed on the respiratory epithelium of human distal airways in 20 lungs removed at operation for the treatment of carcinoma. Using 1 micron araldite sections stained with Toluidine Blue for light microscopy, with further electron microscopic study where required, we have described mast cells in the epithelium of bronchioles, terminal bronchioles, and respiratory bronchioles. Examination of these cells at both microscopic levels demonstrates many of the typical features of mast cells--namely, metachromatic granules on staining with toluidine blue at light microscopic level, surface microvillous processes, and numerous dense intracytoplasmic granules with a whorled substructure at electron microscopy. Furthermore, we have identified cells devoid of granular material which may be recognised as mast cells by virtue of their nuclear and cell surface characteristics--the occurrence of a spectrum of change between those cells devoid of granular material and those with full granule content; and a few cells in which we found both typical dense, whorled granules and large lucent vacuoles devoid of such material. Quantitation of all respiratory epithelial cells by light microscopy shows that mast cells comprise 0-2% of the total population. A higher proportion of mast cells was found in the epithelium of smokers than in non-smokers. Because of the presence of many epithelial mast cells devoid of granule content, we suggest that the use of traditional 4 microns paraffin sections stained with thiazine dyes to study mast cells would lead to a marked underestimation of the epithelial population.

Basophils↗
PubMedDate not supplied

Retinoic acid alters hindbrain Hox code and induces transformation of rhombomeres 2/3 into a 4/5 identity.

It has been suggested that Hox genes play an important part in the patterning of limbs, vertebrae and craniofacial structures by providing an ordered molecular system of positional values, termed the Hox code. Little is known about the nature of the signals that govern the establishment and regulation of Hox genes, but retinoic acid can affect the expression of these genes in cell lines and in embryonic tissues. On the basis of experimental and clinical evidence, the hindbrain and branchial region of the head are particularly sensitive to the effects of retinoic acid but the phenotypes are complex and hard to interpret, and how and if they relate to Hox expression has not been clear. Here we follow the changes induced by retinoic acid to hindbrain segmentation and the branchial arches using transgenic mice which contain lacZ reporter genes that reveal the endogenous segment-restricted expression of the Hox-B1 (Hox-2.9), Hox-B2(Hox-2.8) and Krox-20 genes. Our results show that these genes rapidly respond to exposure to retinoic acid at preheadfold stages and undergo a progressive series of changes in segmental expression that are associated with specific phenotypes in hindbrain of first branchial arch. Together the molecular and anatomical alterations indicate that retinoic acid has induced changes in the hindbrain Hox code which result in the homeotic transformation of rhombomeres (r) 2/3 to an r4/5 identity. A main feature of this rhombomeric phenotype is that the trigeminal motor nerve is transformed to a facial identity. Furthermore, in support of this change in rhombomeric identity, neural crest cells derived from r2/3 also express posterior Hox markers suggesting that the retinoic acid-induced transformation extends to multiple components of the first branchial arch.

Animals↗
PubMedDate not supplied

Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1.

Segmentation of the vertebrate hindbrain into rhombomeres is important for the anterior-posterior arrangement of cranial motor nuclei and efferent nerves. Underlying this reiterated organization, Hox genes display segmentally restricted domains of expression, such as expression of Hoxb-1 (refs 5, 6) in rhombomere 4 (r4). Here we report that absence of Hoxb-1 leads to changes in r4 identity. In mutant mouse embryos, molecular markers indicate that patterning of r4 is initiated properly but not maintained. Cellular analysis by DiI tracing reveals that the r4-specific facial branchiomotor (FBM) and contralateral vestibuloacoustic efferent (CVA) neurons are incorrectly specified. In wild-type mice CVA neurons migrate from r4 into the contralateral side, and we found in lineage analysis that FBM neurons migrate from r4 into r5. In mutants, motor neurons differentiate but the CVA and FBM neurons fail to migrate into their proper positions. Instead, they form a motor nucleus which migrates atypically, and there is a subsequent loss of the facial motor nerve. These results demonstrate that, as a part of its role in maintaining rhombomere identity, Hoxb-1 is involved in controlling migratory properties of motor neurons in the hindbrain.

Animals↗