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Biomedical subjects

D H Brown

Publications and source records attributed to D H Brown.

At least 55 records · Page 3Linked to original sources
PubMed1995

Metal biomonitoring with mosses: procedures for correcting for soil contamination.

Highly variable total concentrations of 15 elements have been found in five species of epigeic mosses growing in remote areas of Italy and in northern Victoria Land (continental Antarctica). It is very likely that soil particles entrapped in the mosses cause these high element concentration differences, thereby leading to inexact interpretations of baseline concentrations and of element distribution in different parts of mosses. A simple procedure for estimating more plausible background values that consists of subtracting the substratum contribution from raw concentrations of elements in mosses is reported. The normalization of total concentrations to the regional soil composition is also emphasized, in order to point out other possible metal sources.

Journal Article↗
PubMed1995

The free flap and plate in oromandibular reconstruction: long-term review and indications.

The purpose of this study was to define the role of reconstruction plates as bone replacement in oromandibular reconstruction. From 1987 through 1991, 71 consecutive oral cancer patients underwent composite resection and reconstruction and were entered into one of two studies. In the first study of 31 patients, 15 underwent oromandibular reconstruction using a radial forearm osteocutaneous flap, while the remainder (16) received a radial forearm fasciocutaneous flap together with a mandibular reconstruction plate. The second study involved 40 subsequent patients, all receiving the latter form of reconstruction. Twenty-one of the plates were stainless steel, and the remaining 19 were of the titanium hollow screw (THORP) type. We followed the patients prospectively. We defined success as a reconstruction that we did not have to remove. Additionally, since the patients had limited life expectancy, we developed the idea of days of life lost and incorporated it into our definition of a successful outcome. Vascularized autogenous bone proved to be more successful than metallic plates used alone in terms both of reconstruction survival and of minimizing days of life lost. The overall success rate of mandibular plate reconstruction was 78.9 percent, but analysis by defect type revealed a failure rate of 35 percent when the defects were anterior and only 5 percent when they were lateral. THORP plates demonstrated a trend towards more durability. We would now recommend plate reconstruction only in lateral defects in patients with a poor prognosis.

Bone Plates↗
PubMed1995

Primary mandibular reconstruction with the titanium hollow screw reconstruction plate: evaluation of 51 cases.

Fifty-one patients undergoing surgical reconstruction of mandibular defects with the titanium hollow screw reconstruction plate over a 4-year period were analyzed. Plate failure was defined as flap necrosis, plate extrusion, or plate fracture necessitating a further surgical procedure and occurred in 12 patients (24 percent). The incidence was highest for patients who had more than three mandibular regions resected. It was not affected by the primary site of the tumor or whether the patient had received radiation therapy. Although the failure rate was the same whether the patient attained full oral function or was fed by gastrostomy, plate fracture was limited to the former group. The overall cause-specific survival rate for this group of patients was 68 and 56 percent at 1 and 2 years, respectively. In addition, 81 percent of patients attained a full oral diet.

Adult↗
PubMed1995

Growth of Mycobacterium tuberculosis in BCG-resistant and -susceptible mice: establishment of latency and reactivation.

Growth of mycobacterial species is controlled by a gene, Bcg (candidate Nramp). Bcg acts at the macrophage level and is thought to control some aspect of macrophage priming for activation. Infection of Mycobacterium bovis BCG-susceptible (Bcgs) mice with several different mycobacterial species results in the growth of the microorganisms, while the growth of the same organisms is controlled in BCG-resistant (Bcgr) mice. The capacity of Bcg to control the growth of M. tuberculosis has not been extensively explored. The purpose of this investigation, therefore, was to compare the growth of M. tuberculosis in Bcgr and Bcgs mice. We found that the growth of tubercule bacilli was different in the lungs and spleens of Bcgr and Bcgs mice when they were inoculated with fewer then 10(3) CFU of the mycobacterium. The differences in growth were more easily distinguished in the lungs then in the spleens. The growth of the microorganisms in both strains of mice peaked between 35 and 43 days, and a latent infection was established by 65 days after infection. Activation of the hypothalamic-pituitary-adrenal axis resulted in reactivation of the growth of M. tuberculosis in both Bcgr and Bcgs mice. Greater numbers of tubercule bacilli were isolated from lungs than from spleens following reactivation. The utility of this mouse model in the study of the establishment of latency and reactivation of M. tuberculosis is discussed.

Animals↗
PubMed1995

Cytokine-mediated activation of macrophages from Mycobacterium bovis BCG-resistant and -susceptible mice: differential effects of corticosterone on antimycobacterial activity and expression of the Bcg gene (Candidate Nramp).

Previous work in our laboratory has shown that corticosterone increases the susceptibility of macrophages from Bcgs mice to the growth of Mycobacterium avium. The innate antimycobacterial activity of macrophages from Bcgr mice was not affected by corticosterone. In contrast to the differential effect of corticosterone on the antimycobacterial activity of the macrophages, corticosterone suppressed the production of tumor necrosis factor alpha and nitric oxide by macrophages from both Bcgr and Bcgs mice. The purpose of this investigation was to compare the effects of corticosterone on the antimycobacterial activity of macrophages from Bcgr and Bcgs mice that have been activated in vitro with recombinant gamma interferon or granulocyte-macrophage colony-stimulating factor. We found that macrophages from both strains of congenic mice responded equally to the activation stimuli. The capacity of the activated macrophages from Bcgs mice to suppress the growth of M. avium was inhibited by the addition of corticosterone to the cultures. The addition of NG-monomethyl-L-arginine to the cultures did not affect the capacity of resident splenic macrophages from Bcgr mice to limit the growth of M. avium. However, NG-monomethyl-L-arginine reduced the capacity of gamma interferon-activated, but not granulocyte-macrophage colony-stimulating factor-activated, macrophages to limit the growth of M. avium by macrophages from both Bcgr and Bcgs mice. The addition of corticosterone suppressed Nramp expression by macrophages from Bcgs mice. Nramp expression by macrophages from Bcgr mice was not affected by corticosterone.

Animals↗
PubMed1995

Assessment and referral patterns of patients admitted after deliberate self-poisoning.

The assessment and referral patterns of adult patients after deliberate self-poisoning in Dundee were examined. Questionnaires were completed by the admitting physicians and assessing psychiatrists over a 3 month period. Demographic data concerning the patients and the nature of self-harm were similar to previous studies. Initial referral rate was 95% but dropped to between 70% and 81% after the post receiving round. Up to 2 hours/day could be required for assessment and 75% of the cases required some form of psychiatric follow-up. Although both groups of doctors considered that the majority of patients required or would benefit from psychiatric referral, there was poor agreement when patients were independently categorised into high or low suicide risk (kappa = 0.04). Agreement was also low regarding whether referral was essential or not (kappa = 0.06). Although junior medical staff can play an important role in screening of patients, the psychiatric service, including trained nurses, may be best placed to provide a full assessment, where required.

Adult↗
PubMed1994

Three-dimensional imaging of the parapharyngeal space.

Recent advances in computer technology have allowed the introduction of workstations into the hospital capable of creating or reconstructing three-dimensional (3-D) models from serial cross sections of an object. These can be obtained from either computed tomography or magnetic resonance imaging scans. The reconstruction is stored in the computer's memory and may be interactively displayed and analyzed. Morphometric parameters may be used to characterize the object; it may be rotated or cut; light sources may be moved to enhance surface detail; or selective translucency can be created--in effect, the volumetric model of the reconstructed object can be explored in detail. Herein we examine the use of 3-D reconstructions of computed tomography and magnetic resonance imaging scans of parapharyngeal space tumors of varying pathologic features, both common and rare. This anatomic region (in which complex spatial relationships are probably best appreciated in 3-D) lends itself to this type of reconstruction. The 3-D reconstructions can be a useful tool for determining and following tumor volumes, and 3-D technology has immediate applications in diagnostic imaging, surgical planning, patient education, and medical research.

Adult↗
PubMed1994

Activation of the hypothalamic-pituitary-adrenal axis differentially affects the anti-mycobacterial activity of macrophages from BCG-resistant and susceptible mice.

The effect of hypothalamic-pituitary-adrenal (HPA) axis activation and exogenous glucocorticoids on the ability of splenic macrophages to control the growth of Mycobacterium avium was evaluated. We found that activation of the HPA axis by restraint stress or the addition of corticosterone increased the susceptibility of macrophages from mice that are innately susceptible to the in vivo growth of M. avium. In contrast, the ability of macrophages from innately resistant, congenic mice to control the growth of M. avium was not affected by HPA activation or the addition of corticosterone. The effect of restraint and of corticosterone on macrophage function was abrogated by either treating mice with the glucocorticoid receptor antagonist RU486 or the addition of the drug to cultures of macrophages. Activation of the HPA axis as well as the addition of corticosterone to cultures of macrophages resulted in a suppression of the production of tumor necrosis factor (TNF)-alpha and of reactive nitrogen intermediates by macrophages from both strains of mice. The lack of effect of HPA activation and of corticosterone on the mycobacterial resistance of macrophages from BCG-resistant mice, while at the same time suppressing the production of reactive nitrogen intermediates, appears to rule out a role for this antimicrobial pathway in innate resistance to mycobacterial growth.

Animals↗
PubMed1994

Rapid conversion to high xanthine oxidase activity in viable Kupffer cells during hypoxia.

It has been widely postulated that the central mechanism of hepatic reperfusion injury involves the conversion, during ischemia, of the enzyme xanthine dehydrogenase (XDH) to its free radical-producing form, xanthine oxidase (XOD). However, this theory has been questioned because (a) XDH to XOD conversion in whole liver occurs very slowly; (b) the cellular distribution of XDH/XOD is unclear; and (c) the direct demonstration of XDH to XOD conversion in viable cells is lacking. In this paper, we address all three issues by measuring XDH to XOD conversion and cell viability in purified populations of hepatic endothelial cells (EC), Kupffer cells (KC), and hepatocytes (HEP). Although XDH/XOD activity on a cellular basis was greater in hepatocytes (0.92 +/- 0.12 mU/10(6) cells) than ECs (0.03 +/- 0.01) or KCs (0.12 +/- 0.04), XDH + XOD specific activity was similar in all three cell types (HEP 1.85 +/- 0.10 U/g protein; EC 1.69 +/- 0.54; KC 2.30 +/- 0.22). Over 150 min of warm (37 degrees C) or 24 h of cold (4 degrees C) hypoxia, percent XOD activity increased slowly in ECs, from 21 +/- 2% (basal) to 39 +/- 3% (warm) and 49 +/- 5% (cold) and in HEPs (29 +/- 2% to 38 +/- 3% and 49 +/- 2%), but converted significantly faster in KCs (28 +/- 3% to 91 +/- 7% and 94 +/- 4%). The dramatic changes in Kupffer cell XOD during cold hypoxia occurred despite only minor changes in cell viability. When hypoxic KCs were reoxygenated after 16 h of cold hypoxia, there was a marked increase in cell death that was significantly blocked by allopurinol. These data suggest that significant conversion to the free radical-producing state occurs within viable KCs, and that Kupffer cell XOD may play an important role in mediating reperfusion injury in the liver.

Animals↗
PubMed1994

How I do it: Zenker's stapler diverticulectomy.

Zenker's diverticulum is an outpouching of the hypopharyngeal mucosa through Killian's area, a dehiscent or weak area between the cricopharyngeus muscle and the inferior constrictor muscle. Although this entity was described more than a century ago, these pulsion diverticuli continue to challenge surgeons to this day. The authors would like to reintroduce a method of resection that has proved useful in our practice.

Esophagoscopy↗
PubMed1994

Complications associated with rigid fixation of mandibulotomies.

The complications associated with the use of rigid internal fixation in 31 consecutive patients who had undergone a mandibulotomy for the treatment of pathology of the oral cavity or oropharynx were reviewed. Rigid fixation was accomplished with two major types of systems: compression plates and reconstruction plates. Complications occurred in 11 patients (35%) with an average of 1.7 complications per patient. Most complications were minor in nature, and were treated successfully with conservative measures. Patients who had preoperative radiotherapy were more likely to develop nonunion and osteoradionecrosis. Plate exposure was the single, most common complication, accounting for 13% of the complications. No major differences were noted in the complication rates between the two systems.

Adult↗
PubMed1994

Bacillary angiomatosis: a new entity in acquired immunodeficiency syndrome.

Since the recognition of the acquired immunodeficiency syndrome (AIDS) in 1981, previously rare infections and neoplasms have become increasingly common. Bacillary angiomatosis, undescribed in the medical literature prior to 1983, is now second in frequency only to Kaposi's sarcoma with respect to the cutaneous manifestations associated with human immunodeficiency virus (HIV) infection. Caused by Rochalimaea henselae, bacillary angiomatosis is easily treated, when diagnosed early, with erythromycin. We present two cases of bacillary angiomatosis that presented to Toronto General Hospital and review this new and clinically interesting entity. The incidence of bacillary angiomatosis will undoubtedly increase as the HIV epidemic accelerates. Since bacillary angiomatosis commonly affects the head and neck region, it is important for the otolaryngologist to become increasingly proficient in its diagnosis and treatment. The current AIDS crisis demands that the otolaryngologist become aware not only of bacillary angiomatosis, but also of the other cutaneous head and neck manifestations of HIV infection.

AIDS-Related Opportunistic Infections↗
PubMed1993

Immunohistochemical analysis of the proliferative capacity of duct and acinar cells during ligation-induced atrophy and subsequent regeneration of rat parotid gland.

To study the proliferative capacity of salivary gland, an animal model of regeneration was developed. A clamp, which induced atrophy in parotid gland by obstructing the main excretory duct but allowed restoration of duct patency following removal, was implanted in a series of rats. When it was removed (Day 7), the weight of the glands was reduced by 50% and acinar cells had decreased from 93.8% to 8.2% of total cell population. Regeneration occurred rapidly following removal of the clamp. The number and location of cycling intercalated, striated, and excretory duct cells and acinar cells were monitored using an antibody to proliferating cell nuclear antigen (PCNA). All cell types were induced to cycle but the predominant cell to cycle was the acinar cell. During regeneration the number of PCNA+ acinar cells increased 38.7-fold from steady-state values. Results demonstrate that acinar cells have a significant potential for cycling, contrary to current histogenetic theories of salivary gland tumourigenesis which exclude acinar cells as potential progenitor cells on the grounds of their putative limited cycling capacity.

Animals↗
PubMed1993

Regulation of mycobacterial growth by the hypothalamus-pituitary-adrenal axis: differential responses of Mycobacterium bovis BCG-resistant and -susceptible mice.

The role of the hypothalamus-pituitary-adrenal (HPA) axis in regulating the growth of Mycobacterium avium in Mycobacterium bovis BCG-resistant and -susceptible congenic mice was evaluated. Restraint was used to activate the HPA axis, which resulted in an increase in the level of corticosterone in the plasma. Activation of the HPA axis increased the susceptibility of BALB/c.Bcgs mice to the growth of M. avium. In contrast, the growth of M. avium was not altered in BALB/c.Bcgr mice as a result of HPA activation. Adrenalectomy abolished the effect of HPA activation on mycobacterial growth, as did treatment of the mice with a glucocorticoid receptor antagonist, RU 486. Activation of the HPA axis also resulted in the increased susceptibility of splenic macrophages from Bcgs mice but not from Bcgr mice to M. avium growth in vitro. The production of tumor necrosis factor alpha and of reactive nitrogen intermediates by splenic macrophages from both strains of mice was suppressed as a result of HPA activation. The implications of these findings for resistance controlled by Bcg and for susceptibility to mycobacterial growth are discussed.

Adrenalectomy↗
PubMed1993

Role of hyperbaric oxygen therapy in the management of mandibular osteoradionecrosis.

Hyperbaric oxygen (HBO) has been used as a tool in the management of osteoradionecrosis (ORN). However, it has not been conclusively proven to be of benefit. The precise role and guidelines for its use also have not been clearly defined. This report retrospectively analyzes 41 patients treated at the Hyperbaric Chamber Unit at the Toronto Hospital (Toronto General Division) with proven mandibular ORN from 1980 to 1985. The results show that 83% of the patients had a significant improvement with HBO therapy, judged by at least a 50% decrease in the size of the exposed bone, closing of the fistulous tract, or complete relief of symptoms. Within the group of patients who were significantly improved, 15% showed complete resolution of ORN. Seven (17%) of the patients did not benefit from the HBO. All seven patients had radiological evidence of dead bone. Based on these observations, the following conclusions can be made: 1. HBO is of benefit in the management of ORN. 2. Patients with ORN may be divided into two groups: mild and severe. 3. Cases of mild ORN will heal with HBO alone, but, in severe ORN, surgery is necessary to remove dead bone. 4. All patients with ORN should receive dental evaluation, local wound care, and a strict oral hygiene regimen. Diseased teeth should be removed prior to radiotherapy. Subsequently, any teeth that became abscessed should be extracted in conjunction with prophylactic HBO. Antibiotics play an ancillary role in the management of ORN. For patients who have received radiation to the mandible, the authors propose regular follow-up in order to detect ORN at a time when HBO can arrest the disease.

Combined Modality Therapy↗
PubMed1993

Classification of mandibular defects.

A classification of mandibular defects based on functional as well as aesthetic factors is presented. By taking into account the difficulties in restoring form and function and not simply relying on traditional anatomic landmarks, it is hoped that this method will allow different types of reconstructions to be fairly evaluated. It also should help surgeons to tailor individual reconstructive techniques to specific clinical situations. Major difficulties in mandibular reconstruction arise when a condyle requires replacement, when there is a mucosal and/or skin component to the defect, and when the area to be reconstructed involves the anterior arch. The classification is based on three upper-case and three lower-case characters: H, C, L and o, m, s. H defects are lateral defects of any length, including the condyle but not significantly crossing the midline; L defects are the same only without the condyle; C defects consist of the entire central segment containing the four incisors and the two canines. Combinations of these letters are possible (an angle-to-angle defect, for example, is represented as LCL). Thus H and L defects may reach or even extend slightly beyond the midline but are not referred to as LC or HC unless they contain the entire central segment. The letters o (neither a skin nor a mucosal component), s (skin), m (mucosa), and sm (skin plus mucosa) are added to denote the epithelial requirement.

Bone Plates↗
PubMed1993

Glossopharyngeal neuralgia and syncope secondary to neck malignancy.

Glossopharyngeal neuralgia with syncope, secondary to a malignant tumor in the neck, is an extremely rare condition. Dysman, et al more recently described a case in 1980. In this case, it was initially difficult to confirm the proper diagnosis since recurrent tumor was not able to be detected either clinically or radiographically. The patient was initially treated as syncope due to hypotension and bradycardia, but pacemaker therapy failed to control the cardiovascular abnormality. The administration of Dilantin, however, seems to improve the neuralgic pain and syncope. Due to a poor prognosis from the neck tumor recurrence, and patient refusal of further therapy, no surgical control of symptoms was attempted in this patient. This report is presented to make otolaryngologists aware of this condition.

Aged↗