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Biomedical subjects

W E Grant

Publications and source records attributed to W E Grant.

At least 19 recordsLinked to original sources
PubMed2001

Influence of acaricide resistance on cattle-fever tick (Boophilus spp.) infestations in semi-arid thornshrublands: a simulation approach.

Cattle-fever tick (Boophilus microplus and B. annulatus) populations that develop acaricide resistance become more difficult to control or eradicate. We used a simulation model to assess the direct and indirect effects of interactions among season, habitat type, grazing strategy, and acaricide resistance on the ability to eradicate Boophilus infestations in semi-arid thornshrublands of Texas, USA. Season of infestation appeared to have the strongest effect, with infestations begun on 27 September (autumn) tending to die out sooner than those begun on 1 March (spring) and to remain undetected. Habitat type had the next strongest effect, with infestations surviving much longer as canopy cover increased from uncanopied buffelgrass (Cenchrus ciliaris) habitats to mesquite (Prosopis glandulosa)-canopied grass habitats. Acaricide resistance had a moderate effect; as expected, highly resistant tick populations survived longer than those with no acaricide resistance. The importance of grazing strategy varied with changes in habitat type: as canopy cover increased, infestation duration increased faster under continuous grazing than under rotational grazing strategies. Importance of grazing strategy also varied with acaricide resistance: detected tick populations with no and slight acaricide resistance subjected to acaricide treatments tended to survive longer under rotational grazing than continuous grazing, due to reduced contact with a treated host. Populations with moderate and high resistance behaved more like untreated populations, tending to survive longer under continuous, rather than rotational, grazing, because they experienced less mortality on a treated host. Assuming acaricide treatments at 2-week intervals and maintenance of cattle in infested pastures, results indicate that, for each habitat type, infesting ticks have a threshold of acaricide resistance below which one can eradicate them faster with continuous grazing than with rotational grazing. As canopy cover increases, this threshold appears to shift from high resistance (in grass) to slight resistance (in mesquite).

Animals↗
PubMed2000

Simulation of rotational grazing to evaluate integrated pest management strategies for Boophilus microplus (Acari: ixodidae) in Venezuela.

Ranchers in Venezuela historically have controlled the cattle-fever tick, Boophilus microplus (Canestrini), with acaricide treatments of cattle but no technical planning. We developed a simulation model to evaluate cattle-tick population dynamics in systematic pasture rotation systems and Integrated Pest Management (IPM) approaches to managing ticks in the tropical dry-forest ecological zone of Venezuela. Model output showed five generations of cattle-ticks produced each year throughout the dry and rainy seasons that occur in this zone. Sensitivity analyses showed disproportionately large changes in on-host B. microplus populations in response to small changes in larval mortality rates, such as those resulting from differences in the innate resistance of cattle to tick parasitism. Simulation results with 1-6 pasture systems suggest that adjusting the graze:rest sequence with systematic rotation among 4-6 pastures could suppress, but not eradicate, tick populations.

Animal Husbandry↗
PubMed1998

KTP laser assisted excision of glomus tympanicum.

A 39-year-old female with a two-year history of mild hearing loss and discomfort on air flight descent was found to have a pulsatile mass behind an intact tympanic membrane. A suspected diagnosis of glomus tympanicum was confirmed by computed tomography (CT) scan imaging. The lesion filled the mesotympanum and hypotympanum but the jugular bony plate was intact, confirming the tympanic site of the lesion. This very vascular tumour was exposed by a tympanomeatal flap and the KTP laser used to shrink and coagulate the tumour progressively with minimal haemorrhage and blood loss. Complete excision of the lesion was achieved without the need for bony removal, and with minimal blood loss. The use of the KTP laser to coagulate this vascular lesion allowed safe removal of the tumour and avoided the need for extended facial recess or hypotympanotomy surgery.

Adult↗
PubMed1997

Photodynamic therapy: an effective, but non-selective treatment for superficial cancers of the oral cavity.

It has often been claimed that photodynamic therapy (PDT) produces selective destruction of small cancers without affecting the adjacent normal tissue. The objective of our work was to treat small cancers of the oral cavity with PDT and subsequently excise the treated areas for histological studies of tumour and adjacent normal tissue exposed to the same light dose. Eleven patients with histologically proven T1NO oral squamous-cell carcinomas were treated with PDT, using Photofrin as a sensitiser. The tumours plus a surrounding cuff of normal tissue were exposed to 50 J/cm2 non-thermal laser light at 630 nm delivered by surface illumination and the treated areas subsequently excised. Histological staining and image analysis were used to determine the nature and extent of injury. No macroscopic distinction was evident between tumour and normal tissue exposed to light. Histologically, replacement of superficial epithelium, tumour and connective tissue with a fibrinous necrotic slough was seen. There was also loss of endothelium from small vessels, with haemorrhage and thrombosis. Preservation of subepithelial collagen and elastin was demonstrated with EVG staining. No evidence of selective tumour necrosis was found. Although depth of injury was variable, full thickness mucosal necrosis occurred in all cases.

Carcinoma, Squamous Cell↗
PubMed1996

Oculopharyngeal myopathy with sensorineural hearing loss.

A case is reported of a 59-year-old Caucasian male with oculopharyngeal myopathy and sensorineural hearing loss. He presented with progressive ptosis, sensorineural hearing loss over several years and symptoms of mild dysphagia. Further enquiry into his family history revealed that every male member in his family that lived beyond the age of 60 exhibited identical symptoms. Symptoms of ptosis and dysphagia are consistent with the rare autosomal dominant condition of oculopharyngeal myopathy, believed to be due to mitochondrial disease. The combination of ptosis, dysphagia and sensorineural hearing loss with normal distant muscle group biopsy has not been described before.

Audiometry, Pure-Tone↗
PubMed1995

Bleeding after tonsillectomy in severe von Willebrand's disease.

A case is reported of a HIV-positive patient with severe von Willebrand's disease describing the bleeding complications during and after tonsillectomy. This patient underwent surgery for asymmetrical tonsillar hypertrophy. The tonsils were spontaneously haemorrhaging and there therefore was a suspicion of neoplasia. Despite close cooperation between the ENT Department and the Haemophilia Centre, involving per-operative Factor VIII monitoring and replacement, the patient suffered both protracted primary and secondary haemorrhages. We report this as a cautionary tale as our previous experience with mild to moderate haemophilia has been uncomplicated, but on this occasion there was massive haemorrhage. We feel that tonsillectomy should not be undertaken in a patient with a severe bleeding disorder without an absolute indicate.

Adult↗
PubMed1995

The effect of photodynamic therapy on the mechanical integrity of normal rabbit carotid arteries.

Photodynamic therapy (PDT) for tumor ablation is effective in the treatment of superficial cancers. Adjunctive intraoperative PDT has been proposed for the "sterilization" of tumor beds after the resection of malignancies. Arteries in photosensitized animal models exposed to appropriate light receive characteristic injury. This study was conducted to determine whether photodynamic injury to the rabbit carotid artery results in thrombotic occlusion or weakening of the vessel wall. PDT of the carotid arteries of New Zealand white rabbits, using either disulphonated aluminum phthalocyanine or 5-aminolevulinic-acid-induced protoporphyrin IX as the photosensitizer, was performed with a light dose of 100 J/cm2. Histologic examination of the carotids treated with either agent demonstrated typical full-thickness loss of cellularity 3 days after PDT. All vessels remained patent, and no inflammatory infiltrate was evident. Elastin van Gieson staining showed preservation of inner and medial elastic laminae and medial and adventitial collagen. Additional rabbits were similarly treated with PDT to 1-cm segments of both common carotid arteries. The animals were sacrificed at 3, 7, and 21 days. The carotids were exposed, and both control and treated segments were subjected to intraluminal hydrostatic distention until the vessels burst. No reduction in the pressure required to burst the vessels was evident in the treated vessels as compared with the control vessels. The authors of the study concluded that despite full-thickness cell death, PDT-treated arteries are not at risk for thrombotic occlusion or hemorrhage.

Aluminum↗
PubMed1995

The role of forensic anthropology in the recovery and analysis of Branch Davidian Compound victims: techniques of analysis.

The recovery and analysis of human remains from the Branch Davidian Compound, Mount Carmel, Texas, was a multidisciplinary team effort. This presentation deals with one aspect of the forensic anthropological contribution to this collaborative endeavor--the examination and inventory of human skeletal remains and the interpretation of these osteological data. Briefly described first are the content and format of the skeletal inventory and the examination procedures used for data collection. Two subsequent sections illustrate the use of these data to determine (a) age, sex, ancestry, stature, and other distinguishing characteristics, and (b) the presence and nature of any premortem, perimortem, and postmortem trauma. The next section shows how these findings assist in establishing positive identification through, for example, comparison with medical, dental, and other background records, especially comparison of premortem and postmortem radiographs of bones or dentition. In this context, we consider also the sorting of commingled remains, which includes preliminary assessment of rapidly decomposing remains prior to autopsy to preserve information crucial to identification.

Adolescent↗
PubMed1994

Photodynamic therapy of normal rat arteries after photosensitisation using disulphonated aluminium phthalocyanine and 5-aminolaevulinic acid.

Photodynamic therapy of cancer exposes adjacent arteries to the risk of injury and the possibility of haemorrhage and thrombosis. The nature of photodynamic injury to normal arteries has not been satisfactorily defined, and the ability of arteries to recover with time is unclear. To clarify these issues, we have investigated the effects of PDT on rat femoral arteries, using a second-generation photosensitiser, disulphonated aluminium phthalocyanine, and a new method of photosensitisation, using endogenous synthesis of protoporphyrin IX following systemic administration of 5-aminolaevulinic acid (ALA). Pharmacokinetic studies of sensitiser fluorescence were carried out to determine peak levels of sensitiser. Subsequently photodynamic therapy at times corresponding to maximal fluorescence was performed using two light doses, 100 and 250 J cm-2. The nature of injury sustained and recovery over a 6 month period was investigated. Three days following PDT, all vessels treated showed complete loss of endothelium, with death of all medial smooth muscle cells, leaving an acellular flaccid artery wall. No vascular occlusion, haemorrhage or thrombosis was found. A striking feature was the lack of inflammatory response in the vessel wall at any time studied. Re-endothelialisation occurred in all vessels by 2 weeks. The phthalocyanine group showed repopulation of the media with smooth muscle cells to be almost complete by 3 months. However, the ALA group failed to redevelop a muscular wall and remained dilated at 6 months. Luminal cross-sectional area of the ALA-treated group was significantly greater than both control and phthalocyanine groups at 6 months. All vessels remained patent. This study indicates that arteries exposed to PDT are not at risk of catastrophic haemorrhage or occlusion, a finding that is of significance for both the local treatment of tumours and the use of PDT as an intraoperative adjunct to surgery for the ablation of microscopic residual malignant disease.

Aminolevulinic Acid↗
PubMed1993

Photodynamic therapy of oral cancer: photosensitisation with systemic aminolaevulinic acid.

Photodynamic therapy with intravenous photosensitising drugs has been shown to be effective in the ablation of superficial cancers, but long-lasting photosensitivity is a serious disadvantage. Similar photosensitivity is a feature of certain types of porphyria. We present the first report of tumour necrosis brought about by photodynamic activation of a temporary endogenous porphyrin accumulation, after an oral dose of the haem precursor, 5-aminolaevulinic acid. In 4 patients, quantitative fluorescence microscopy showed that accumulation of the photoactive intermediate protoporphyrin IX peaked after 4-6 h in 4 oral cavity squamous cell carcinomas, returning to background in 24 h. Irradiation with non-thermal red laser light caused tumour necrosis in 3 patients.

Administration, Oral↗
PubMed1993

Photodynamic therapy of malignant and premalignant lesions in patients with 'field cancerization' of the oral cavity.

The management of patients with 'field cancerization' of the oral mucosa, with multicentric foci of invasion, presents a considerable problem for the head and neck surgeon. Surgical resection of synchronous or metachronous primary squamous cell carcinomas, along with adjacent premalignant lesions, is likely to be associated with considerable mutilation. Photodynamic therapy (PDT) has been shown to be of value in the treatment of superficial tumours in the upper aerodigestive tract, with excellent healing of treated areas. This study reports the use of PDT to treat 11 patients with 'field cancerization' occurring in the oral cavity. Six patients had multiple primary cancers and five had single primary tumours. All had associated areas of leukoplakia. Each received Photofrin 2 mg/kg 48 hours prior to photoirradiation with 50-100 J/cm2 red laser light by surface illumination. Six to eight weeks later treated areas in 10 of the 11 patients showed a complete response to PDT; one patient had areas of residual leukoplakia. Two patients developed further areas of leukoplakia or erythroplakia within 12 months but no patient has had evidence of recurrent invasive carcinoma in the treated areas. Longer term follow-up will be necessary to exclude further recurrence. It is concluded that PDT offers an effective repeatable treatment option, whether on its own or as an adjunct to local excision, for patients with 'field cancerization' of the oral cavity.

Carcinoma, Squamous Cell↗
PubMed1993

Computed tomography-pathologic assessment of laser-induced necrosis in rat liver.

RATIONALE AND OBJECTIVES: Interstitial laser photocoagulation (ILP) causes localized tissue necrosis. This study was performed to determine 1) whether the changes seen on computed tomography (CT) correspond to the necrosis pathologically, and 2) which CT technique best shows the necrosis. METHODS: Eighteen Wistar rats had ILP to their liver using a neodymium yttrium aluminum garnet [Nd:YAG] laser. Radio-opaque markers attached to the liver defined an imaging plane. Precontrast "dynamic" and delayed CT scans were performed. The size of necrosis was measured on CT, and macroscopically after resecting the liver. Computed tomography density numbers were measured from the necrotic area and normal liver for each CT technique. RESULTS: There was a good correlation between the necrosis size on CT and pathologically (P < .001). Maximum lesion-to-liver contrast was obtained on "dynamic" CT scans. CONCLUSIONS: The extent of tissue density changes on CT in rat liver after ILP match the extent of necrosis seen pathologically. The best CT technique use assessed for evaluating laser-induced liver necrosis is dynamic contrast-enhanced scanning.

Animals↗
PubMed1991

Stapedius tendon ossification: a rare cause of congenital conductive hearing loss.

Two cases are presented of bilateral conductive deafness in siblings. An initial presumptive diagnosis of otosclerosis was made in the first case, that of a nine-year-old girl with a bilateral hearing loss of 45 dB. Exploratory tympanotomy revealed normal ossicles but the stapedius 'tendon' was found to be a solid bony bar fixing the stapes. Division of the 'tendon' resulted in normal ossicular mobility and return of hearing with closure of the air-bone gap. Identical ossification was found in her other ear, and some years later in both ears of one of her brothers. Similar surgery restored hearing successfully in each case. An acquired aetiology has been proposed in one of the three previously reported cases; this report, however, suggests the congenital nature of the anomaly. No previous cases have been described occurring in siblings.

Adult↗
PubMed1989

Seasonal variation in serum testosterone, testicular measurements and semen characteristics in the collared peccary (Tayassu tajacu).

Blood samples and testicular measurements were obtained from 4-8 captive adult collared peccaries monthly for 18 months and from wild adult males during summer (N = 16) and winter (N = 22) seasons. Serum concentrations of testosterone were determined by radioimmunoassay. Semen samples were collected monthly by electroejaculation from captive males for 1 year. Serum testosterone concentrations and testicular measurements varied in a low-amplitude circannual pattern, with maximum mean testosterone concentrations in fall and winter (1150-1400 pg/ml) and minimum values in summer (500-700 pg/ml). Circannual rhythms appeared to be related to dominance. Serum testosterone levels in wild males generally were lower than in captive males, although this difference was not significant (P greater than 0.05). Semen characteristics did not exhibit a circannual rhythm. These results suggest that the male peccary remains reproductively fertile throughout the year, yet may undergo a facultative summer quiescence influenced by ambient temperature and social factors.

Animals↗
PubMed1988

Indices for physiological assessment of nutritional condition in pregnant collared peccaries (Tayassu tajacu).

Hematological and serum biochemical responses to two levels of dietary energy (high energy [HE], 3300 kcal digestible energy [DE]/kg; moderate energy [ME], 2300 kcal DE/kg) and protein (high protein [HP], 16.0% crude protein; moderate protein [MP], 8.4% crude protein) during gestation in 15 collared peccaries (Tayassu tajacu) were examined. Dietary energy and protein levels influenced body weight gain during gestation. Red blood cell counts and lymphocyte concentrations were higher and neutrophil concentrations were lower among females fed an HP diet compared to those fed an MP diet. Alkaline phosphatase and alpha-2 globulin concentrations were higher among females fed an MP diet. Aspartate aminotransferase and cholesterol concentrations were higher and calcium and thyroxine concentrations were lower among females fed ME diets compared to those fed HE diets. These results suggest that physiological indices used in combination with morphological measurements can be useful in assessing collared peccary nutritional health during gestation.

Animals↗