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Biomedical subjects

J A Cameron

Publications and source records attributed to J A Cameron.

At least 19 recordsLinked to original sources
PubMed2000

Extent of ossification at the amputation plane is correlated with the decline of blastema formation and regeneration in Xenopus laevis hindlimbs.

Xenopus laevis larvae gradually lose the ability to regenerate lost hindlimb structures as they progress through metamorphosis. Previous studies have suggested that this loss of regenerative capacity occurs in a proximal-to-distal fashion. We assessed the quality of overall regeneration and early bud blastema formation in order to evaluate previous explanations for this loss of regenerative ability in Xenopus. We further examined the extent to which epidermis, basement membrane, dermis, cartilage, bone, periosteum, and accumulated mesenchyme within the blastema are involved in the decline of regenerative abilities during mid-metamorphic stages of development. Each tissue was scored based on its contributions to the regeneration blastema, in accordance with previously reported blastemal descriptions. Tadpoles amputated at the ankle and tarsal-metatarsal joints scored objectively higher within the overall regeneration and blastema quality rating systems. Both joint sites met more criteria associated with regeneration-capable blastemas than tadpoles amputated through the middle of the tarsus, especially at later stages of metamorphosis. The three amputation sites studied began to vary in their ability to regenerate skeletal elements and to generate productive blastemas during the same stages at which we initially observed ossification of the tarsus. These results suggest that the decline of Xenopus hindlimb regeneration does not occur in a strictly proximal-to-distal fashion but rather is dependent at later stages on the state of ossification of the structure through which amputation occurs. Our morphological and cellular observations reveal specific times and places during Xenopus hindlimb development at which further investigations into tissue-specific molecular events during early regeneration should be focused.

Amputation, Surgical↗
PubMed2000

Inhibition of nitric oxide synthesis potentiates hypertension during chronic glucose infusion in rats.

Endothelial dysfunction has been proposed to contribute to impaired blood flow control or hypertension in many conditions characterized by hyperinsulinemia or hyperglycemia. However, most studies have focused on whether endothelial dysfunction is present in the established phases of these various hypertensive states, and there is little known concerning the role of the endothelium in the initial stages. This study tested whether nitric oxide production, before endothelial dysfunction develops, plays an important role in counteracting the hypertensive response to chronic glucose infusion. Glucose was infused (18.6 mg/kg per minute IV) for 7 days in 8 normal rats (G) and in 9 rats with a long-term background intravenous infusion of N(G)-nitro-L-arginine methyl ester (L-NAME) at 10 microg/kg per minute (G+L). Mean arterial pressure (MAP), measured 24 hours per day, increased an average of approximately 11 mm Hg in the G rats. L-NAME treatment increased MAP an average of 28+/-2 mm Hg in the G+L rats, and glucose infusion raised MAP >30 mm Hg above that, averaging 155+/-8 mm Hg by day 6. In addition, heart rate increased from an average of 389+/-8 bpm to 441+/-16 bpm by day 6, whereas there was no significant change in the G rats. Glomerular filtration rate decreased significantly with L-NAME treatment and decreased in both groups by day 3 of glucose infusion, reaching lower levels in the G+L rats. These results show that NO is required to minimize the increase in MAP during glucose infusion and suggest that renal and neural mechanisms may be important in mediating that effect.

Animals↗
PubMed2000

Physiological responses associated with sustained delivery of T, DHT, and AED in male rats.

The factors responsible for the marked gender difference in the risk of coronary heart disease and remain controversial. Several clinicians and basic scientists support the hypothesis that a protective effect of endogenous estrogen is the key, however epidemiological data failed to prove this trend. The role of endogenous androgens or sex steroid hormones on the development of atherosclerosis has received little attention over the years. The specific objectives of this study are: 1) to deliver testosterone (T), dihydrotestosterone (DHT), or androstenedione (AED) at sustained levels by tricalcium phosphate lysine (TCPL) ceramic delivery devices, and 2) to quantify major biochemical markers levels such as lactate dehydrogenase activity (LDH), total cholesterol, thiobarbituric reactive species associated with sustained delivery of androgens and 3) to evaluate the histopathological changes in vital and reproductive organs associated with excess androgens delivery in adult intact male rats. A total of sixteen male rats were randomly divided into four equal groups. Rats in group I served as intact controls, and animals in groups II-IV were implanted with a single TCPL delivery device contained T (40 mg), DHT (40 mg), or AED (40 mg), respectively. Animals in all groups were weighed and blood was drawn biweekly for cholesterol, LDH and TBAR analysis. At the end of ninety days post implantation, the animals were sacrificed and the organs removed, processed embedded, sectioned and screened for morphological changes. The results of this study suggest that: 1) sustained deliver of androgens caused a statistically significant increase (p < 0.05) in the prostate and the seminal vesicle weights, while the epididymis weights remained similar to control intact animals, 2) decreases in adrenal gland weight was detected in animals treated with androgens compared to control animals, 3) kidney weights increased in all androgen groups compared to control, 4) no differences were observed in heart, spleen, or body weights between the groups, 5) TBAR analysis, as well as LDH activity were not different between androgen treated animals and control animals, and 6) total cholesterol was significantly reduced in T and DHT treated groups compared with control and AED treated animals. The decrease in total cholesterol and reduction in adrenal gland weight may suggest impairment of cholesterol synthesis. In conclusion, this study provides information on the effects of sustained release of DHT, T and AED on the reproductive organs, vital organs, as well as physiological parameters such as TBARS (cellular damage) and total cholesterol.

Androstenedione↗
PubMed1999

Inhibition of calcium ATPase by phencyclidine in rat brain.

Phencyclidine (PCP) is a potent psychotomimetic drug of abuse and has profound effect on the functioning of the central nervous system (CNS). Many of the CNS functions are known to be mediated by calcium (Ca2+). In the present study we have investigated the effects of PCP on Ca2+ ATPase activity in rat brain both in vitro and in vivo. For in vitro studies, synaptic membrane fractions prepared from normal rat brain were incubated with PCP at different concentrations (25-100 microM) before the addition of substrate. For in vivo studies, rats were treated with a single moderate dose of PCP (10 mg/kg, i.p.) and animals were sacrificed at 1,2, 6 and 12 h after treatment. Ca2+ ATPase activity in synaptic membrane fractions was assayed by estimation of inorganic phosphate. PCP inhibited the Ca2+ ATPase in vitro in a concentration dependent manner with significant effect at 50 and 100 microM. A significant time-dependent reduction of the Ca2+ ATPase activity was evident in vivo. As early as 2 h after the treatment of rats with PCP the ATPase activity was significantly reduced. The reduction of Ca2+ ATPase observed even at 12 h after treatment suggesting a prolonged presence of the drug in the brain tissue. Further, kinetic studies in vitro indicated PCP to be a competitive inhibitor of Ca2+ ATPase with respect to the substrate, ATP. The present findings indicate that PCP inhibits synaptic membrane Ca2+ ATPase thus altering cellular Ca2+ homeostasis in CNS which may partially explain the pharmacological effects of the drug and/or its neurotoxicity.

Animals↗
PubMed1999

Presurgical evaluation of the motor hand area with functional MR imaging in patients with tumors and dysplastic lesions.

PURPOSE: To test an optimized functional magnetic resonance (MR) imaging procedure to depict the motor hand representation area (HRA) in patients with epilepsy lesions near the central sulcus. MATERIALS AND METHODS: Fast low-angle shot MR imaging was performed with an oblique single-section imaging technique in eight control subjects (10 hemispheres) and six patients (12 hemispheres). Three series of five activation images (obtained while subjects performed repetitive finger-to-thumb opposition movements) and five rest images were acquired. Each hemisphere was studied in three adjacent sections. Difference maps (obtained with simple subtraction between activation and rest images) were compared with t-test maps. RESULTS: In control subjects, the HRA was visible in 27 of 30 sections. Qualitatively, activation was seen better on t-test maps in 14 and on difference maps in four of these sections. In all patients, motor activation could be seen in the hemisphere that contained the lesion. This activation was considered normal in four patients. In two patients, the HRA was deformed. Functional MR imaging activation in the motor area was confirmed with Penfield stimulation in five patients. CONCLUSION: Functional MR imaging findings in the preoperative assessment of dysplastic lesions around the central sulcus are the same as for tumors. t-test maps are superior to difference maps in the treatment of motor functional MR imaging data.

Adult↗
PubMed1999

Tendinosis and tears of gluteus medius and minimus muscles as a cause of hip pain: MR imaging findings.

OBJECTIVE: This study was conducted to determine the prevalence of tendinosis and tears of gluteus medius and minimus muscles in patients presenting with buttock, lateral hip, or groin pain; describe the MR imaging findings; and discuss their probable relationship to the greater trochanteric pain syndrome. SUBJECTS AND METHODS: Two hundred fifty MR imaging examinations of the hip were performed for the evaluation of buttock, lateral hip, or groin pain. The findings were reviewed for changes in the morphology or signal intensity of gluteus medius and minimus muscles and tendons and for any peritendinous abnormality including distention of regional bursae. RESULTS: Thirty-five studies met our criterion of showing either tendinosis or tears of gluteus medius and minimus muscles as the primary positive finding. Eight patients had complete retracted tears of the gluteus medius, and 14 patients had partial tears; in 13 patients, MR findings were consistent with tendinosis. The gluteus minimus muscle was also involved in 10 patients. MR imaging findings were the same as those described for tears and tendinosis of other regions of the body. Surgical proof of a tendon tear was obtained in six patients. CONCLUSION: Tendinopathy of the hip abductors and gluteus medius and minimus muscles was a common finding on MR imaging in our patients with buttock, lateral hip, or groin pain. Tendinopathy is probably a frequent cause of the greater trochanteric pain syndrome, a common regional pain syndrome that can mimic other important conditions causing hip pain including avascular necrosis and stress fracture. Moreover, it is likely that trochanteric bursitis is associated with tendinopathy.

Arthralgia↗
PubMed1998

Phencyclidine block of Ca2+ ATPase in rat heart sarcoplasmic reticulum.

Phencyclidine hydrochloride (PCP) also known as Angel Dust is a very potent psychotomimetic drug of abuse. Besides its central nervous system (CNS) effects PCP produces a number of adverse effects in a variety of tissues including the cardiovascular system. Since PCP is known to alter the cellular calcium homeostasis the present studies were initiated to determine the changes in cardiac Ca2+ ATPase activity in rats treated with PCP. For in vitro studies the cardiac sarcoplasmic reticulum (SR) fractions prepared from normal rats were incubated with 25, 50 and 100 microM PCP and the enzyme activities were estimated. Whereas, for in vivo studies the cardiac SR fractions prepared from rats treated with PCP (10 mg/kg body wt. single dose, intra-peritoneally (i.p.)) and sacrificed at different time intervals were used. PCP reduced the Ca2+ ATPase activity significantly both in vitro and in vivo. A 50% inhibition of the enzyme activity was obtained with 100 microM PCP in vitro. A significant reduction of SR Ca2+ ATPase was also evident as early as 1 h after treatment of rats with PCP. The reduction of Ca2+ ATPase activity in SR was irreversible even at 12 h after treatment. The in vitro kinetic studies revealed that PCP was found to be a competitive inhibitor of Ca2+ ATPase with respect to the substrate, ATP, and non-competitive with respect to Ca2+ activation. These results indicate that PCP alters the myocardial Ca2+ homeostasis by inhibiting the Ca2+ ATPase in cardiac SR in rats. Inhibition of SR Ca2+ ATPase may result in the impairment of contraction and relaxation coupling processes in the myocardium.

Animals↗
PubMed1998

Endophthalmitis cluster from contaminated donor corneas following penetrating keratoplasty.

OBJECTIVE: To attempt to identify common events or factors in four cases of endophthalmitis that developed after penetrating keratoplasty performed within a 1-week interval. DESIGN: Case series. SETTING: Tertiary care eye hospital in Riyadh, Saudi Arabia. PATIENTS: Four patients in whom endophthalmitis developed after penetrating keratoplasty performed in May 1993. OUTCOME MEASURES: Source of donor tissue, transportation of corneas, handling of corneas at the eye hospital, and causative organism and sensitivity profile. RESULTS: The donor tissue in all four cases originated from the same eye bank. Organisms were cultured from 10 of the 11 donor rims from eye bank A tissue used during the week in question. The causative organisms were Enterococcus faecalis in three patients and Torulopsis glabrata in one patient. In each case the same organism was cultured from the recipient eye and the corresponding donor rim. Two of the four patients had a favourable outcome. CONCLUSIONS: Donor rim culture is essential if the cause of endophthalmitis after penetrating keratoplasty is to be determined. Close communication between eye bank personnel, the microbiology laboratory and the operating surgeon is important as it may influence early detection, choice of treatment and outcome of endophthalmitis after penetrating keratoplasty. Epidemiologic studies from both the source eye bank and the recipient facility are required to fully investigate the cause of a cluster of endophthalmitis cases from contaminated donor tissue following penetrating keratoplasty.

Adult↗
PubMed1996

Reducing the anxiety of children undergoing surgery: parental presence during anaesthetic induction.

OBJECTIVE: The primary aim was to determine whether child anxiety could be reduced by the presence of a parent during anaesthetic induction. Secondary aims involved clarification of the effect of the timing of parental separation, the use of premedication, the seriousness of the surgical procedure, and the flow-on effect of parental anxiety on the level of child anxiety. METHODOLOGY: Subjects were obtained by approaching all parents of children aged from 1 to 8 years admitted for day surgery to a private hospital in Adelaide, South Australia during a 3 month period. Data pertaining to 74 children, representing a response rate of 80.4%, were obtained. Parents were instructed to rate the anxiety of their child for the period immediately prior to separation, and to then rate their own anxiety for the same period of time. RESULTS: Children accompanied during induction were less anxious than those who were not accompanied. Contrary to the belief that child anxiety might be reduced by allowing separation in the theatre holding bay area, it was demonstrated that child anxiety was higher in this group than when separation occurred in the ward. No relationship between premedication or operation severity and either child or parental anxiety was observed. However, parental anxiety was noted to be a significant predictor of child anxiety. Suggestions for a more detailed examination of the relationship between child and parental anxiety in future research were outlined. CONCLUSIONS: It was concluded that there are benefits in allowing parents to be present during anaesthetic induction. However, the potential negative effect of parental anxiety must be acknowledged before parents are allowed to accompany their child as a matter of course.

Analysis of Variance↗
PubMed1996

Recurrence of climatic droplet keratopathy. Two case reports.

Climatic droplet keratopathy (CDK) is characterized by a band-shaped pattern of subepithelial opacities and golden-yellow spherules. Recurrence of this disease in corneal grafts has not been reported. We report two cases that developed recurrence of this disease in corneal grafts done for CDK, 3 1/2 years following lamellar penetrating keratoplasty and 6 years following penetrating keratoplasty. This illustrates the possibility of this degenerative disease to recur in a few years if aetiological factors are persistently present.

Cornea↗
PubMed1996

Increase in brain nitric oxide synthase activity in daunorubicin-treated rats.

Anthracyclines such as daunorubicin are very effective anticancer agents. These drugs are known to cause side effects including cardiotoxicity. Anthracyclines are neurotoxic to laboratory animals. Nitric oxide is a novel and very important chemical messenger in the brain. However, at higher levels, nitric oxide causes well defined neurotoxicity. Therefore, we determined nitric oxide synthase activity in rat brain after daunorubicin treatment in an effort to explain the neurotoxicity produced by anthracyclines. Male Sprague-Dawley rats were treated with different subcutaneous doses of daunorubicin (0.1-4.0 mg/kg/week for five weeks) while control animals were injected with phosphate buffered saline. There was a significant increase (80%) of nitric oxide synthase activity in daunorubicin-treated animals as compared to controls. This activity was inhibited by N-monomethyl-L-arginine (NMMA), nitroarginine, N-6-aminohexyl-5-chloro-1-napthalene sulfonamide (W-7), a calmodulin antagonist, suggesting that the nitric oxide synthase activity is calmodulin dependent. Further, our in vitro studies demonstrated that daunorubicin interacted with calmodulin as measured by N-phenyl-1-napthylamine (NPN) fluorescence. These results indicate that daunorubicin increases nitric oxide synthase activity in rat brain which may increase the levels of nitric oxide. The increased levels of nitric oxide may cause neurotoxicity. Our results further indicate that daunorubicin interacts with calmodulin and enhances nitric oxide synthase activity which is dependent on calmodulin.

Animals↗
PubMed1996

Fusarium polycaprolactone depolymerase is cutinase.

Polycaprolactone (PCL), a synthetic polyester, is degraded by a variety of microorganisms, including some phytopathogens. Many phytopathogens secrete cutinase, a serine hydrolase that degrades cutin, the structural polymer of the plant cuticle. We compared wild-type strains and a cutinase-negative gene replacement mutant strain of Fusarium solani f. sp. pisi (D. J. Stahl and W. Schäfer, Plant Cell 4:621-629, 1992) and a wild-type strain of Fusarium moniliforme to show that Fusarium cutinase is a PCL depolymerase. The wild-type strains, but not the mutant strain, (i) degraded PCL and used it as a source of carbon and energy, (ii) showed induction of secreted PCL depolymerase and an esterase activity of cutinase when grown in the presence of cutin, and (iii) showed induction of PCL depolymerase and an esterase activity of cutinase when grown in the presence of a hydrolysate of PCL, which contains PCL oligomers that are structurally similar to the natural inducers of cutinase. These results together with other details of regulation and conditions for optimal enzyme activity indicate that the Fusarium PCL depolymerase, required for degradation and utilization of PCL, is cutinase.

Biodegradation, Environmental↗
PubMed1995

Pyogenic granulomas of the cornea.

BACKGROUND: Pyogenic granulomas are vascular inflammatory lesions that represent an aberrant wound healing response. They typically arise from mucous membranes or skin. Pyogenic granulomas primarily involving the cornea have been rarely reported. METHODS: Between January 1983 and July 1994, 14 patients with histologically proven pyogenic granulomas of the cornea were treated. RESULTS: The precipitating event was a persistent epithelial defect in nine patients. Ocular surface disease was present in all patients. Predisposing conditions included indolent corneal ulceration, cry eye syndrome, trachoma, trichiasis, alkali burn, multiple topical drug use, previous orbital irradiation, and ocular cicatricial pemphigoid. CONCLUSIONS: Ophthalmologists should be aware that pyogenic granulomas may involve the cornea and include this entry in the differential diagnosis of tumors involving the limbus or cornea. The typical clinical appearance, rapid growth, minimal staining with rose bengal dye, response to topical steroids, and associated ocular surface disease help to distinguish this lesion from a neoplastic epithelial tumor of the conjunctiva or cornea.

Adolescent↗
PubMed1995

Shield ulcers and plaques of the cornea in vernal keratoconjunctivitis.

BACKGROUND: Shield-shaped corneal ulcers and plaques are serious sight-threatening corneal manifestations of vernal keratoconjunctivitis. There are few reports describing the management of these patients and their outcomes. METHODS: The clinical presentation, treatment, and outcome of 66 shield ulcers and/or plaques in 55 eyes of 41 patients with vernal keratoconjunctivitis were studied in this retrospective study of patients treated at King Khaled Eye Specialist Hospital during an 11-year period. RESULTS: Patients with shield ulcers where the base of the ulcer was transparent usually had rapid re-epithelialization and an excellent visual outcome with medical treatment alone. Patients with shield ulcers and visible plaque formation had delayed re-epithelialization when receiving only medical treatment. Complications of delayed re-epithelialization consisted of bacterial keratitis in five eyes, amblyopia in one eye, and strabismus in one patient. CONCLUSIONS: Patients with shield ulcers and/or plaques that do not re-epithelialize once active vernal keratoconjunctivitis has been controlled should have surgical intervention. In this series, a simple scraping of the base and margins of the ulcer with removal of the inflammatory material (i.e., the plaque) resulted in rapid re-epithelialization in 20 of 23 ulcers and plaques. An algorithm for treating shield ulcers and/or plaques is presented based on the experience at this institution.

Administration, Topical↗