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Biomedical subjects

G H Collins

Publications and source records attributed to G H Collins.

At least 37 records · Page 2Linked to original sources
PubMed1994

Antemortem diagnosis of Baló concentric sclerosis: correlative MR imaging and pathologic features.

PURPOSE: To report a case of a rare demyelinating disease called Baló concentric sclerosis. MATERIALS AND METHODS: A 32-year-old woman had left hemiparesis that progressed to hemiplegia, hemihypesthesia, and left hemianopsia. Laboratory evaluation was notable only for a mildly elevated erythrocyte sedimentation rate and an elevated level of myelin basic protein in cerebrospinal fluid. RESULTS: The antemortem diagnosis was made on the basis of magnetic resonance (MR) imaging of the brain, which showed numerous areas of concentric demyelination alternating with "spared" white matter. With the exception of a temporary improvement with high-dosage intravenous steroid therapy, the clinical course was monophasic and relentless, leading to death approximately 1 year after the onset of symptoms. Pathologic examination helped confirm the diagnosis. CONCLUSION: Because MR imaging shows alternating ringlike lesions involving the deep and superficial white matter, which correspond to pathologic findings, it may play a central role in antemortem diagnosis of this rare disease, leaving more invasive diagnostic procedures for evaluation of equivocal cases.

Adult↗
PubMed1994

Demyelinating and gliotic cerebellar lesions in Langerhans cell histiocytosis.

PURPOSE: To describe the involvement of the cerebellum by a gliotic and demyelinating process in Langerhans cell histiocytosis. METHODS: A retrospective analysis of all (N = 30) cases of Langerhans cell histiocytosis followed at our institution since 1975 yielded four patients with CT and/or MR evidence of cerebellar abnormalities. RESULTS: Four patients manifested strikingly similar findings of symmetric nonenhancing hypodensities in the dentate nuclei region of the cerebellum, which were hypointense on short-repetition-time/short-echo-time MR and hyperintense on long-repetition-time/long-echo-time MR. Biopsy in one patient yielded areas of demyelination, cell loss, and gliosis without histiocytic infiltration. CONCLUSION: Langerhans cell histiocytosis involves the cerebellum in a specific and poorly understood manner. Lesions on imaging may precede clinical findings by years. Lesions may occur in patients who have never experienced radiation therapy and may act as a marker for eventual central nervous system deterioration.

Biopsy↗
PubMed1993

Comparative pharmacokinetic behaviour of albendazole in sheep and goats.

Albendazole (ABZ) containing a trace of [14C]-ABZ was administered intraruminally at 4.75 mg kg-1 to Merino sheep and Angora goats and the pharmacokinetic behaviour of ABZ and its metabolites in plasma nd abomasal fluid compared. The systemic availability (area under the curve, AUC) for total [14C]-labelled metabolites was significantly lower in goats than in sheep. This was largely attributable to the disposition of ABZ sulphoxide (ABZ.SO) which had a significantly lower maximum concentration (Cmax) in goats (0.94 +/- 0.04 micrograms ml-1) than in sheep (1.41 +/- 0.24 micrograms ml-1). The AUC of [14C] in abomasal fluid was similar in goats and sheep, with approximately 35 and 45% of the dose passing the pylorus in the two species, respectively. ABZ, ABZ.SO and ABZ sulphone (ABZ.SO2) were present in the abomasal fluid of both species but between-species differences were only evident with ABZ.SO which had a lower Cmax in goats compared with sheep. The relative proportions of the [14C] dose excreted in urine and faeces were similar between species. It is suggested that ABZ may be sequestered to a greater extent in the liver of goats than of sheep which would result in lower concentrations of ABZ.SO in plasma and abomasal fluid. This behaviour might be compensated for by administering ABZ to goats at a proportionally higher dose rate.

Abomasum↗
PubMed1993

Comparative kinetic disposition of oxfendazole in sheep and goats before and during infection with Haemonchus contortus and Trichostrongylus colubriformis.

The kinetic disposition of [14C]-oxfendazole (OFZ) and its metabolites, fenbendazole (FBZ) and fenbendazole sulphone (FBZ.SO2), in plasma and abomasal fluid were determined in Merino sheep and Angora goats before and during infection with Trichostrongylus colubriformis and Haemonchus contortus. The systemic availability (area under the plasma curve, AUC) of OFZ was significantly lower in goats (13.5 micrograms.h/ml) than in sheep (22.2 micrograms.h/ml) and was reduced with infection in goats (5.6 micrograms.h/ml) and sheep (15.1 micrograms.h/ml). The elimination of plasma [14C] was faster in goats than in sheep. The responses observed for [14C] were a reflection of the behaviour of OFZ. The concentration of OFZ and metabolites in abomasal fluid were similar in both species in the absence or presence of infection. However, as the mean flow rate of abomasal fluid was slower in goats (240 ml/h) than in sheep (488 ml/h), only 7% of the dose passed the pylorus in abomasal fluid of goats compared with 14% in sheep. The presence of gastrointestinal nematodes generally increased abomasal fluid flow rate but neither species nor infection had any effect on the rate or extent of [14C] excretion in urine or faeces. It is suggested that goats possess a faster hepatic metabolism than sheep resulting in more rapid elimination of OFZ.

Abomasum↗
PubMed1993

Comparative pharmacokinetic disposition of closantel in sheep and goats.

The pharmacokinetic disposition of closantel was examined following intraruminal (i.r.) or intramuscular (i.m.) administration to adult Merino sheep and to adult and 3-month-old, suckling Angora goats. In adult goats the maximum concentration (Cmax) and area under the plasma concentration with time curve (AUC) following 3.75, 7.5 and 15.0 mg closantel/kg given i.r. increased with dose however the time of Cmax (Tmax = 2.6d) in plasma was unaffected by dose rate. The elimination phase (K10) of closantel was monoexponential with a half-life (t1/2) of 4.7d again unaffected by dose rate. Apart from a more rapid absorption phase and earlier Tmax following 3.75 mg closantel/kg i.m., pharmacokinetic behaviour was similar to that following i.r. administration at 3.75 or 7.5 mg/kg. Although absorption rate was more rapid in kids after i.r. administration at 7.5 mg/kg, pharmacokinetic disposition of closantel was otherwise similar to that in adult goats. No closantel was detected in milk of treated doses or in the plasma of their kids. I.R. closantel at 7.5 mg/kg was more slowly absorbed in goats than in sheep but Cmax was similar in both species. However, K10 t1/2 was significantly shorter in goats (4d) than in sheep (14d). Faster elimination resulted in an almost three-fold lowering of AUC in goats and could dramatically reduce the sustained action of closantel in this species compared with sheep.

Absorption↗
PubMed1992

An association of faecal egg counts and prolactin concentrations in sera of periparturient Angora goats.

Faecal egg counts and serum prolactin concentrations in 13 pregnant and five non-pregnant Angora goats were monitored over a period of 20 weeks. The mean weekly egg counts of pregnant goats were significantly higher (P less than 0.01) than those of non-pregnant goats. In pregnant goats the mean egg counts in the 6 week post-partum period were significantly higher (P less than 0.01) than those of 6 weeks prepartum. The mean prolactin concentration of pregnant goats during the 6 week post-partum period was significantly higher (P less than 0.01) than that of 6 weeks pre-partum. During the 6 to 3 weeks before parturition, the prolactin values generally remained low (below 100 ng ml-1). The rise in prolactin concentration started between 3 weeks and 1 week before parturition. Only in pregnant goats was there a positive linear regression between prolactin levels and faecal egg counts.

Animals↗
PubMed1991

Effects of cholinergic drugs on longitudinal contraction in levamisole-susceptible and -resistant Haemonchus contortus.

A novel force transducer was used to measure the effects of cholinergic agonists on longitudinal contraction in Haemonchus contortus. Drugs were applied to whole worms or injected via a cannula in the pseudocoelomic cavity. A number of agonists, including nicotine and the anthelmintics m-aminolevamisole, levamisole and morantel, caused contractions in whole worms. Four- to 25-fold increases in concentration of the active compounds were required to cause contractions in each of two levamisole-resistant strains of H. contortus. Of the other compounds tested, bephenium had equivalent activity against susceptible and resistant strains. Anticholinesterase compounds caused contractions after a slight delay in susceptible, but not resistant worms. Numerous cholinergic agonists and other compounds did not cause contraction when applied to whole worms. One of these, acetylcholine, caused contractions in cannulated worms. Compared with the susceptible strain, five- to six-fold higher concentrations of acetylcholine were required to cause equivalent contractions in the resistant strains. Levamisole resistance in adult H. contortus is likely to be due to a change in the characteristics of the cholinergic receptor(s).

Animals↗
PubMed1991

Epidemiology of paramphistomosis in cattle.

The epidemiology of paramphistomosis in cattle was studied using tracer calves in a subtropical location in eastern Australia. Two species of paramphistomes were present; Calicophoron calicophorum and Paramphistomum ichikawai. The former species was the most abundant. Gyraulus scottianus and Helicorbis australiensis acted as intermediate hosts, respectively. Paramphistome burdens varied seasonally and were dependent upon the number of infected host snails. Peak fluke burdens and clinical paramphistomosis occurred in late summer in year 1 and early winter in year 2. The peak fluke burdens coincided with prolonged inundation of the grazing areas resulting in rapid multiplication and infection of host snails, and the period after the inundated areas dried out. The prevalence of infection in snails was high in both years, peaking at 98% in year 1 and 58% in year 2. The main host snail, G. scottianus, aestivated and retained infection for at least 24 weeks in soil, and in vegetable debris on the surface of the soil, resulting in rapid reappearance of host snails and infective metacercariae after the onset of seasonal rain. Metacercariae survived on herbage for up to 12 weeks, depending on the environmental conditions. Paramphistome burdens in calves could be predicted from the prevalence of infection in the host snail, the water levels and an index of surface water on the grazing site. Control of paramphistomosis during and after flooding may be achieved by removal of susceptible cattle from pasture or regular treatment during these periods. Strategic treatment during the dry season may reduce contamination of snail habitats and infectivity of the pasture in the following wet season.

Animals↗
PubMed1991

Disposition of oxfendazole in goats and efficacy compared with sheep.

The disposition of intraruminally administered oxfendazole (OFZ) in goats was studied at 5, 10 and 20 mg kg-1. The area under the plasma concentration with time curve (AUC) increased with increasing dose but at a declining rate. AUC was lower after intra-abomasal compared with intraruminal administration. OFZ was less effective against drug resistant Trichostrongylus colubriformis in goats than in sheep but was of similar efficacy against drug resistant Haemonchus contortus in both host species. In the same experiment peak plasma levels of OFZ in goats were about half those in sheep given the same dose. Of 70 goats tested in the field, total rumen bypass occurred in 12 per cent and partial bypass in 67 per cent. Lower systemic availability due to bypass would be expected to reduce further anthelmintic efficacy in goats. From the results of these experiments a dose rate of 10 mg kg-1 is recommended for goats. When given at this rate as a divided dose at 12 hourly intervals over 24 hours, OFZ was significantly more effective than a single dose in reducing egg counts.

Animals↗
PubMed1991

Changes in liveweight gain and blood constituents in experimental infection of goats with a goat-derived compared with a sheep-derived strain of Haemonchus contortus.

Two groups of goats were experimentally infected with two different strains of Haemonchus contortus and compared with the controls. Group A animals were infected with a goat-derived strain (GDS) while Group B animals were infected with a sheep-derived strain (SDS). Changes in the liveweights and some blood constitutents between the two infected groups were compared. The pathogenic effects of the GDS larvae were generally more serious when compared with those of the SDS larvae.

Animals↗
PubMed1991

Haematological and pathological responses to experimental Trixacarus caviae infection in guinea pigs.

Outbred guinea pigs became infected with the mite Trixacarus caviae (Acarina, Sarcoptidae) when introduced into an infected colony. Mite numbers were highest after one month, then fell progressively. Infected guinea pigs developed a neutrophilia, monocytosis, eosinophilia and basophilia. Despite pronounced reactive changes in the superficial lymph nodes, infected guinea pigs developed only a mild dermatitis. In contrast, home bred animals, susceptible to T. caviae acquired many mites and developed a severe chronic dermatitis. Trixacaral manage in guinea pigs offers considerable potential for the study of mite infections in man and animals.

Animals↗
PubMed1991

Relationship of Wallerian degeneration to regrowing axons.

Because Wallerian degeneration constitutes a highly significant and unavoidable position in the sequence of nervous system regeneration we have extended our observations regarding this process as it occurs in our cryogenic model of spinal cord injury in the rat. In previous studies we have observed essentially no growth into the Wallerian zone despite a significant amount of axonal regrowth through the injured region. In the present study we have examined by electron microscopy the Wallerian degeneration and its interface with the axons from the injured region. In the Wallerian region our observations have not only confirmed those of many previous investigators but have suggested an orderly sequence of changes during the first 60 days post-injury, beginning with relative tissue preservation followed by depletion of degenerating axoplasm, extracellular deposition of myelin and the development of a cellular reaction. Associated with the cellular reaction is the development of large astrocytic cells which can be found adjacent to unmyelinated and thinly myelinated axons. With this limited evidence of support for axonal growth in the Wallerian zone it is suggested that further expansion of this cellular matrix should provide significant support to regrowing axons.

Animals↗
PubMed1991

Dirofilaria immitis in cats from inner Sydney.

Two hundred feral cats from the inner suburbs of Sydney were examined post mortem for adult Dirofilaria immitis and circulating microfilariae, and 101 of these cats were tested for heartworm antigens by an ELISA. Only 2 cats (1%) had adult heartworms, the blood sample from another cat contained a single microfilaria. The blood of a further three cats contained small amounts of D immitis antigen. Although D immitis occurs in cats in Sydney, the prevalence is not high enough to warrant prophylactic treatment.

Animals↗
PubMed1990

The establishment and development of Haemonchus contortus in goats.

Twelve goats were inoculated with 40,000 third-stage Haemonchus contortus larvae and two were killed on each of Days 4, 7, 11, 14, 18 and 21 after inoculation (DAI). The number of worms that established, and the site of development were recorded. More worms established in the fundic, than in the middle or pyloric thirds of the abomasum. Early development occurred within the mucosa; emergence into the lumen started between 7 and 11 days after infection. By 4 DAI, all worms had completed the third moult to the L4 stage. At 11 DAI the majority of the worms were adults. A mean of 13.2% of the female worms had eggs in their uteri at 18 DAI; by 21 DAI more than half of the female worms had eggs in their uteri. The development of H. contortus was essentially similar to that described in sheep.

Abomasum↗
PubMed1990

The establishment and development of Trichostrongylus colubriformis in goats.

Twelve goats were inoculated with 20,000 infective larvae of Trichostrongylus colubriformis and two were killed on each of Days 4, 7, 11, 14, 18 and 21 after inoculation (DAI). The number of worms that established, and the site of development were recorded. Most of the worms established within the first 3 m of the small intestine. There was little relocation or loss of nematodes after establishment. The worms started to migrate from the mucosa to the lumen 11 days after infection. At 4 DAI, 63% of the worms were still at the late L3 stage; the remainder of the worm population had completed the third moult to the L4 stage. The population at 11 DAI comprised largely young adults. When 21 DAI was reached, about 57% of the female worms had eggs in their uteri.

Abomasum↗