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Biomedical subjects

G H Collins

Publications and source records attributed to G H Collins.

At least 55 records · Page 3Linked to original sources
PubMed1990

Seasonal variations in the populations of infective larvae on pasture and the numbers of nematode eggs in the faeces of farmed goats.

The levels of nematode egg production in goats and the availability of infective larvae (L3) on pasture were investigated on a dairy unit in New South Wales, Australia. The output of eggs by adult goats was always above 300 epg. The profile of the graph of larval availability in herbage paralleled those for temperature and rainfall, suggesting that larval peaks occurred when the temperature and availability of moisture were optimal. The dominant genus was Trichostrongylus, followed by Haemonchus, then Ostertagia. A larger proportion of Haemonchus larvae in the cultures of faeces were collected during the summer months.

Animals↗
PubMed1989

Trixacarus caviae infection of guinea pigs with genetically determined differences in susceptibility to Trichostrongylus colubriformis infection.

Guinea pigs with genetically determined resistance or susceptibility to infection with the nematode parasite Trichostrongylus colubriformis were allowed to become infected with the sarcoptid mite Trixacarus caviae. Compared with nematode-susceptible guinea pigs, nematode-resistant animals had larger populations of mites and developed a more severe dermatitis, with greater mast cell hyperplasia and many more infiltrating eosinophils. The results suggest that animals bred for resistance to one parasite may have greater susceptibility to other parasites.

Animals↗
PubMed1989

Glial activity during axonal regrowth following cryogenic injury of rat spinal cord.

The cryogenic model of spinal cord injury is associated with regrowth of axons through a zone of injury which is composed of a complex matrix of intact blood vessels, cells and extracellular materials. We have used this, therefore, as a means for studying the relationship between these cellular components, particularly the astrocytes, and the regrowing axons. For the time period of 60 days following injury we have found that, from an undifferentiated group of cells which appears early, there develops a population of astrocytes which is associated with the restoration of neural structure, including the return of axons, to the damaged area. We interpret these associations to be supportive through direct axonal interactions and indirect environmental contributions.

Animals↗
PubMed1989

Prospects for axonal regrowth in spinal cord injury.

Some of the evidence relating to the possible cellular relationships in regenerating mammalian central nervous tissue is reviewed. From this review it is suggested that data do exist which reveal a potential for regeneration based upon the basic properties and behavior of axons and glial cells. Models of tissue injury which optimize these intrinsic capabilities may generate significant information about the regenerative possibilities of central nervous tissue.

Animals↗
PubMed1989

Cellular changes during repair of a cryogenic spinal cord injury in the rat: an electron microscopic study.

Cryogenic injury of adult, rat spinal cord was produced under controlled non-invasive conditions to study repair and regeneration in adult, mammalian central nervous tissue in which tissue continuity and integrity are relatively preserved. Under these experimental conditions axons and myelin are destroyed, a matrix of glial cells is preserved, and regrowth of axons is apparent. Electron microscopic studies at 7, 15, 30 and 60 days post-injury demonstrate axonal structures indicative of regrowth, astrocytic structures which appear to provide support to both matrix and axons and myelination of axons by both oligodendrocytes and Schwann cells. These cellular events restore much of the normal structure within the injured area up to its junction with the Wallerian zone. In this junctional zone morphologic evidence may indicate continuing cellular activity, even at 60 days, in axons, astrocytes and myelinating cells. These studies suggest that under ideal conditions damaged axons may be capable of regeneration within the adult mammalian central nervous system and that this model provides an opportunity to define some of the mechanisms.

Animals↗
PubMed1987

Systemic noninflammatory vasculopathy with prominent CNS involvement--a case report.

This is a case report of a thirty-seven-year-old man with systemic noninflammatory vasculopathy who developed a slowly progressive dementia with multiple sites of stroke. Cerebral angiography revealed abnormal terminal vasculature with beading and occlusions. Brain biopsy confirmed a noninflammatory vascular pathology. We have also reviewed the world literature relevant to this clinicopathologic entity and have discussed its relationship to thromboangiitis obliterans cerebri.

Adult↗
PubMed1986

The histopathology of freezing injury to the rat spinal cord. A light microscope study. I. Early degenerative changes.

In an effort to develop a method of tissue injury which would provide a model for the study of axonal regrowth in adult mammalian central nervous system (CNS), we have analyzed the effects of freezing in the dorsal columns of more than 200 rat spinal cords. The effects of temperature and time of exposure upon the size, shape, distribution and histologic characteristics of the lesion have been assessed during the first seven days following the injury. The upper threshold for injury occurs at -3 degrees C for 15 minutes. Between -3 degrees C and -12 degrees C the tissue changes vary in extent and characteristics. Selective damage to axons and myelin occurs with sparing of the supportive cells followed by proliferation of a cellular matrix. At seven days, the lesions produced by -8 degrees C for 15 to 60 minutes have neither axons nor myelin sheaths and consist of a dense cellular matrix of macrophages and presumed glial cells. With these tissue characteristics, and the preservation of tissue continuity without obstructive barriers, this model would appear to be potentially suitable for the study of axonal regrowth potential in mammalian CNS.

Animals↗
PubMed1986

The histopathology of freezing injury to the rat spinal cord. A light and electron microscope study. II. Repair and regeneration.

We utilized a recently developed model of spinal cord injury in which freezing of the rat dorsal column produced axonal injury with sparing and proliferation of the supporting tissue. We examined the progress of the reparative and regenerative processes for 15, 30 and 60 days after the injury. In transverse and sagittal sections at the proximal middle, and distal injury zone and at the zone of Wallerian degeneration we have demonstrated an apparent outgrowth of axons which makes its appearance between 15 and 30 days following injury and increases in amount between 30 and 60 days. The myelination of these fibers is bimodal with Schwann cells predominating in the subpial region, and oligodendrocytes in the deeper regions. Growth into the Wallerian zone is significantly less but does occur at 30 days increasing only slightly at 60 days despite extensive clearing of the breakdown products. We believe that the conditions created by this method of injury provide a suitable model for the study of repair and regeneration of mammalian central nervous tissue.

Animals↗
PubMed1986

Theileria ornithorhynchi Mackerras, 1959 in the platypus, Ornithorhynchus anatinus (Shaw).

Blood smears from 54 platypuses in southeastern Australia were examined by light microscopy. Protozoa were found in erythrocytes in 53 platypuses; all infections were sparse. A few parasites were found in leukocytes. Intraerythrocytic forms examined by electron microscopy contained vacuoles, micronemes, rhoptries and cytostomes with double unit membranes. Merozoites were identified in leukocytes. The parasites were identified as Theileria ornithorhynchi Mackerras, 1959.

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