Biomedical subjects

M J Allen

Publications and source records attributed to M J Allen.

At least 55 records · Page 3Linked to original sources

PubMed1998

Telemedicine in Nova Scotia: report of a pilot study.

OBJECTIVE: To provide and evaluate telemedicine services for rural physicians and patients in Nova Scotia. MATERIALS AND METHODS: As a pilot project, three telemedicine services (videoconference continuing medical education [CME], teledermatology, and teleradiology) were provided to four hospitals in Nova Scotia communities. All four sites received CME (a total of 269 physicians, 53 other health care professionals); three sites received teledermatology (66 consultations), and two sites received teleradiology (808 radiologic examinations). At the consulting site, 12 faculty members presented 24 one-hour videoconferences, and there was one consulting radiologist and dermatologist. Each service was evaluated independently. Methods included participant questionnaires; focus groups; numbers and categories of participants or examinations; comparison of operational costs, capitol costs (teledermatology and teleradiology), and travel costs (CME); technical assessments of hardware, software, and telecommunications; assessment of clinical diagnostic procedures (teledermatology); and comparative study of original and digitized films (teleradiology). RESULTS: Despite growing pains, the technologies effectively provided the three services: the services were acceptable to referring and consulting physicians and patients. Improvements in patient care and outcomes comparable to those of traditional methods were demonstrated in teleradiology and teledermatology, especially for emergencies. Physician access to CME and patient access to dermatology consultation services were improved. Financial savings were demonstrated for CME, but further investigation is required to determine the savings attributable to teleradiology and teledermatology. CONCLUSIONS: The telemedicine services supported rural physicians, their patients, and their communities. Although telemedicine is not a panacea for all concerns of rural physicians, the pilot project provided a strong foundation for further development and study.

Adolescent↗

PubMed1998

Stabilization of Aspergillus awamori glucoamylase by proline substitution and combining stabilizing mutations.

To stabilize Aspergillus awamori glucoamylase (GA), three proline substitution mutations were constructed. When expressed in Saccharomyces cerevisiae, Ser30-->Pro (S30P) stabilized the enzyme without decreased activity, whereas Asp345-->Pro (D345P) did not significantly alter and Glu408-->Pro (E408P) greatly decreased enzyme thermostability. The S30P mutation was combined with two previously identified stabilizing mutations: Gly137-->Ala, and Asn20-->Cys/Ala27-->Cys (which creates a disulfide bond between positions 20 and 27). The combined mutants demonstrated cumulative stabilization as shown by decreased irreversible thermoinactivation rates between 65 and 80 degrees C. Additionally, two of the combined mutants outperformed wild-type GA in high-temperature (65 degrees C) saccharifications of DE 10 maltodextrin and were more active than the wild-type enzyme when assayed using maltose as substrate.

Amino Acid Substitution↗

PubMed1998

Serum markers of bone metabolism in dogs.

OBJECTIVE: To establish reference values for a panel of serum markers of bone turnover in dogs of various ages. ANIMALS: Dogs in 4 age groups (0 to 1 year; 1 to 2 years; 3 to 7 years; > 8 years). PROCEDURE: Serum concentrations of the carboxyterminal propeptide of type-I procollagen (PICP) and the aminoterminal propeptide of type-I procollagen (PINP), both markers of type-I collagen synthesis (hence, bone formation), were measured by use of commercial human radioimmunoassay kits. Serum concentrations of the carboxyterminal cross-linked telopeptide of type-I collagen (ICTP), a marker for type-I collagen breakdown (hence, bone resorption), also were measured by use of a commercial human radioimmunoassay kit. Serum osteocalcin (OC) concentrations and alkaline phosphatase (ALP) isoenzyme activities were measured by use of techniques developed specifically for dogs. RESULTS: As expected, the highest values for all of the markers were found in young dogs (< 12 months old). Concentrations of OC and ICTP decreased with age, and were lowest in dogs > 8 years old. Total ALP and bone-specific ALP activities initially decreased with age, then increased in dogs > 8 years old. CONCLUSIONS AND CLINICAL RELEVANCE: Serum markers of bone turnover may be useful diagnostic and prognostic tools for management of dogs with musculoskeletal disorders.

Aging↗

PubMed1997

AFM analysis of DNA-protamine complexes bound to mica.

A novel method for reconstituting sperm chromatin was used to investigate how protamine 1 condenses DNA. Complexes formed in vitro using linearized plasmid DNA were imaged and measured by atomic force microscopy (AFM). The structures formed were found to be highly dependent on the sample preparation method used for reconstitution. Interstrand, side-by-side fasiculation of DNA and toroidal-like structures only 1-2 DNA diameters thick were observed for complexes formed in solution following direct mixing of the DNA and protamine. Large chromatin aggregates were also observed on the mica. However, if the DNA was first allowed to attach to the mica prior to addition of the protamine, well-defined toroidal complexes were formed without any observed DNA fasiculation or aggregate formation. The diameter of the toroids measured 30.6-50.2 nm (mean 39.4 nm). The dimensions of these structures indicate that the condensed DNA is stacked vertically by four to five turns, with each coil containing as little as 360-370 bp of 'B'-form DNA. This approach for preparing and imaging DNA-protamine complexes permits the analysis of intermediate structures 'trapped' on the mica as partially formed toruses of nucleoprotamine.

Aluminum Silicates↗

PubMed1997

Properties of biomolecules measured from atomic force microscope images: a review.

AFM images can be used to obtain quantitative or qualitative information about the properties of biomaterials. Examples presented here are: (1) Persistence length measurements of moving and stationary DNA molecules. (2) Force mapping to measure properties such as the elasticity of cells and vesicles. (3) Phase mode imaging to detect variations in materials and properties of the sample surface. (4) Imaging of surfaces at different constant forces.

Animals↗

PubMed1997

Primary care physicians and coronary heart disease prevention: a practice model.

Primary care physicians have an important role in coronary heart disease prevention. This paper discusses the results of a qualitative study conducted with Nova Scotian physicians to explore the following: physicians' expectations about their role in prevention; obstacles to providing preventive care; and, mechanisms by which preventive care occurs. The second part of the paper presents a practice model which is intended as a framework by which physicians may more effectively educate and counsel their patients about health issues, such as coronary heart disease.

Coronary Disease↗

PubMed1997

Pro-inflammatory cytokines and the pathogenesis of Gaucher's disease: increased release of interleukin-6 and interleukin-10.

Gaucher's disease is characterized by hepatosplenomegaly, bone-marrow infiltration, osteonecrosis and bone thinning, associated with the presence of pathological macrophages that contain undegraded glycosphingolipids. To investigate the possible role of cytokines in the systemic and local manifestations of established Gaucher's disease, interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF alpha) and interleukin-10 (IL-10) were measured in freshly-separated serum. Samples from eight male and 14 female patients with type 1 Gaucher's disease were compared with sera from 22 healthy age- and sex-matched controls. Concentrations of IL-6 and IL-10 were significantly elevated in sera from patients with Gaucher's disease (11.9 +/- 1.8 (SEM) pg/ml and 5.4 +/- 0.5 (SEM) pg/ml, respectively) compared with those of controls (4.1 +/- 0.9 (SEM) and 0.8 +/- 0.3 (SEM) pg/ml, p < 0.0001). No significant differences in concentrations of TNF alpha or IL-1 beta were identified. IL-6 has been implicated in the development of localized osteolysis in multiple myeloma and in the development of post-menopausal osteoporosis. High concentrations of IL-6 in the serum of patients with Gaucher's disease may thus reflect the development of the bone lesions commonly associated with this disorder. Since IL-6 and IL-10 are important regulators of lymphocyte growth and differentiation, and IL-6 concentrations were significantly raised in patients with oligo- or polyclonal increases in serum immunoglobulins, enhanced release of these cytokines from pathological macrophages provides a pathological link between Gaucher's disease and associated lympho-proliferative disorders.

Adult↗

PubMed1997

Atomic force microscope analysis of chromatin volumes in human sperm with head-shape abnormalities.

We used the atomic force microscope to perform volume measurements on individual human sperm nuclei under ambient conditions. Data obtained for normal sperm and for sperm from seven of the nine classes of head-shape abnormality revealed that the nuclear volumes were essentially identical for sperm in each headshape class, even though the projected areas and shapes of the nuclei have were shown to vary widely. These results indicate that the abnormal sperm head morphologies found at a rate of 25-40% in fertile males are not caused by factors that affect the volume of sperm chromatin, such as the DNA content of the sperm nucleus, differences in chromatin organization, or the extent of DNA compaction.

Cell Nucleus↗

PubMed1997

The role of bone scintigraphy and plain radiography in intractable plantar fasciitis.

The objective of this study was to assess the role of bone scintigraphy and plain film radiography in intractable plantar fasciitis. The bone scintigrams, radiographs and clinical histories of 33 patients with chronic plantar fasciitis were reviewed. These patients were refractory to conservative treatments and were being considered for surgical plantar fascia release. Twenty-eight patients had increased uptake on scintigraphy at the medial calcaneal tubercle, while a plantar spur was seen in 21 patients. Seventy-five percent of patients with increased uptake had a calcaneal spur; 95% of patients with a spur had increased uptake on scintigraphy. It would appear that plantar calcaneal spurs are more prevalent in this group of patients than in the general population and, although they may not be the primary cause of pain, they may predispose to it. Scintigraphy was helpful in patients without a spur or with atypical symptoms or signs. It did not provide any further information on the group of patients with a spur.

Adult↗

PubMed1997

The effects of particulate cobalt, chromium and cobalt-chromium alloy on human osteoblast-like cells in vitro.

Particulate wear debris can induce the release of bone-resorbing cytokines from cultured macrophages and fibroblasts in vitro, and these mediators are believed to be the cause of the periprosthetic bone resorption which leads to aseptic loosening in vivo. Much less is known about the effects of particulate debris on the growth and metabolism of osteoblastic cells. We exposed two human osteoblast-like cell lines (SaOS-2 and MG-63) to particulate cobalt, chromium and cobalt-chromium alloy at concentrations of 0, 0.01, 0.1 and 1.0 mg/ml. Cobalt was toxic to both cell lines and inhibited the production of type-I collagen, osteocalcin and alkaline phosphatase. Chromium and cobalt-chromium were well tolerated by both cell lines, producing no cytotoxicity and no inhibition of type-I collagen synthesis. At the highest concentration tested (1.0 mg/ml), however, chromium inhibited alkaline phosphatase activity, and both chromium and cobalt-chromium alloy inhibited osteocalcin expression. Our results clearly show that particulate metal debris can modulate the growth and metabolism of osteoblastic cells in vitro. Reduced osteoblastic activity at the bone-implant interface may be an important mechanism by which particulate wear debris influences the pathogenesis of aseptic loosening in vivo.

Alkaline Phosphatase↗

PubMed1996

Extent of sperm chromatin hydration determined by atomic force microscopy.

Volume measurements were performed on intact bull and mouse sperm heads and amembranous sperm nuclei, both in the fully hydrated (fluid cell) and dehydrated (air-dried on glass coverslips) states by atomic force microscopy (AFM). Data were obtained by analyzing a small population of cells/nuclei, as well as by performing repeated measurements on single cells imaged following the addition of increasing concentrations of propanol. Results show that the volume of fully hydrated, intact sperm heads and amembranous sperm chromatin particles are at least twice the volume of their air-dried counterparts. Dehydration occurs rapidly in air, and the reduction in volume of chromatin induced by water loss appears to be completely reversible. These studies demonstrate that both mouse and bull sperm chromatin are extensively hydrated in the native state, and are not as compact as previous studies have suggested.

1-Propanol↗

PubMed1996

Sildenafil, a novel effective oral therapy for male erectile dysfunction.

OBJECTIVES: To determine the efficacy and safety of sildenafil, a novel orally active inhibitor of the type-V cyclic guanosine monophosphate-specific phosphodiesterase (the predominant isoenzyme in the human corpus cavernosum) on penile erectile activity in patients with male erectile dysfunction of no established organic cause. PATIENTS AND METHODS: Twelve patients (aged 36-63 years) with male erectile dysfunction of no established organic cause were entered into a double-blind, randomized, placebo-controlled, crossover study which was conducted in two phases. In the first phase (four-way crossover), treatment efficacy was evaluated by measurements of penile rigidity using penile plethysmography during visual sexual stimulation at different doses of sildenafil (10, 25 and 50 mg or placebo). In the second phase (two-way crossover), efficacy was assessed by a diary record of penile erectile activity after single daily doses of sildenafil (25 mg) or placebo for 7 days. RESULTS: The mean (95% confidence interval, CI) duration of rigidity of > 80% at the base of the penis was 1.3 min (0.4-3.1) in patients on placebo, 3.5 min (1.6-7.3; P = 0.009) on 10 mg, 8.0 min (3.7-16.7; P = 0.003) on 25 mg and 11.2 min (5.6-22.3; P < 0.001) on 50 mg of sildenafil. The mean (95% CI) duration of rigidity of > 80% at the tip of the penis was 1.2 min (0.4-2.7) on placebo and 7.4 min (2.4-8.5; P = 0.001) on 50 mg sildenafil. From the diary record of daily erectile activity, the mean (95% CI) total number of erections was significantly higher in patients receiving sildenafil was 6.1 (3.2-11.4), compared with 1.3 (0.5-2.7) in those on placebo; 10 of 12 patients reported improved erectile activity while receiving sildenafil, compared with two of 12 on placebo (P = 0.018). Six patients on active treatment and five on placebo reported mild and transient adverse events which included headache, dyspepsia and pelvic musculo-skeletal pain. CONCLUSION: These results show that sildenafil is a well tolerated and effective oral therapy for male erectile dysfunction with no established organic cause and may represent a new class of peripherally acting drug for the treatment of this condition.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed1996

Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction.

Sildenafil (Viagra, UK-92,480) is a novel oral agent under development for the treatment of penile erectile dysfunction. Erection is dependent on nitric oxide and its second messenger, cyclic guanosine monophosphate (cGMP). However, the relative importance of phosphodiesterase (PDE) isozymes is not clear. We have identified both cGMP- and cyclic adenosine monophosphate-specific phosphodiesterases (PDEs) in human corpora cavernosa in vitro. The main PDE activity in this tissue was due to PDE5, with PDE2 and 3 also identified. Sildenafil is a selective inhibitor of PDE5 with a mean IC50 of 0.0039 microM. In human volunteers, we have shown sildenafil to have suitable pharmacokinetic and pharmacodynamic properties (rapid absorption, relatively short half-life, no significant effect on heart rate and blood pressure) for an oral agent to be taken, as required, prior to sexual activity. Moreover, in a clinical study of 12 patients with erectile dysfunction without an established organic cause, we have shown sildenafil to enhance the erectile response (duration and rigidity of erection) to visual sexual stimulation, thus highlighting the important role of PDE5 in human penile erection. Sildenafil holds promise as a new effective oral treatment for penile erectile dysfunction.

Administration, Oral↗

PubMed1996

The chromatin structure of well-spread demembranated human sperm nuclei revealed by atomic force microscopy.

The fundamental structure formed when genomic DNA is packaged by protamine in the human sperm nucleus still remains essentially unresolved. It is known that the binding of protamine, a small arginine-rich protein, to DNA generates a large dense, hydrophobic complex making the sperm chromatin structure difficult to study microscopically. To visualize the internal nuclear structures, isolated human sperm nuclei were swollen extensively in saline buffer using only a reducing agent. The nuclei were swollen during deposition onto coverglass and then imaged in the atomic force microscope (AFM). The two main results obtained from imaging individual well-spread nuclei indicate that native human sperm chromatin is: (1) particulate, consisting primarily of large nodular structures averaging 98 nm in diameter, and (2) also composed of smaller, nucleosome-like particles observed to form linear chains near the nuclear periphery. These two types of chromatin particles imaged by AFM are remarkably similar to other AFM measurements made on native and reconstituted sperm and somatic chromatin.

Cell Nucleus↗

PubMed1995

Enthalpy of antibody--cytochrome c binding.

High-sensitivity titration calorimetry is used to measure changes in enthalpy, heat capacity, and protonation for binding of two monoclonal antibodies (MAbs) to topologically distinct surfaces of cytochrome c. MAb 2B5 binds near the exposed heme crevice in a reaction involving proton uptake, while there is no change in protonation for MAb 5F8 binding to the opposite side of the molecule. Both antibodies have association rate constants with the activation enthalpy and viscosity dependence expected of diffusion-limited reactions [Raman et al. (1992) Biochemistry 31, 10370-10379], and bind with high affinity (delta Gzerob = -12.6 kcal mol-1 for MAb 2B5 and -13.9 kcal mol-1 for MAb 5F8, at pH 7, 25 degrees C). At 25 degrees C, the equilibrium enthalpy and entropy contributions to the free energy of binding are negative for both antibodies (delta Hzerob = -21.0 kcal mol-1, delta Szerob = -28.2 cal mol-1 K-1 for MAb 2B5; and delta Hzerob = -21.7 kcal mol-1, delta Szerob = 26.3 cal mol-1 K-1 for MAb 5F8). The enthalpy of MAb 2B5-cytochrome c association exhibits a marked temperature dependence (delta Cp = -580 cal mol-1 K-1), but the enthalpy for MAb 5F8 binding is much less dependent on temperature (delta Cp = -172 cal mol-1 K-1). The large differences in delta Cp for binding of the two antibodies suggest corresponding differences in the mode of binding, or in the molecular surfaces buried in the binding reactions. In particular, factors other than hydrophobic effects may be significant contributors to the thermodynamics of antibody-cytochrome c binding, especially when delta Cp is small (MAb 5F8).

Antibodies, Monoclonal↗

PubMed1995

Beta 2-adrenoceptors mediate a reduction in endothelial permeability in vitro.

The permeability of bovine pulmonary artery endothelial (CPAE) monolayers to Evans blue-labelled albumin (Evans blue-albumin) has been measured in vitro. Thrombin caused a concentration-dependent increase in Evans blue-albumin clearance across endothelial monolayers. Isoprenaline inhibited thrombin-induced Evans blue-albumin clearance in a concentration-dependent manner (EC50 21 nM). This effect was mimicked by the selective beta 2-adrenoceptor agonists salbutamol (EC50 64 nM) and salmeterol (EC50 2.7 nM), but not by the selective beta 1-adrenoceptor agonist, RO-363 ((1-[3',4'-dihydroxyphenoxy]-2-hydroxy-[3",4"- dimethoxyphenethylamino]-propane)oxalate), nor by the selective beta 3-adrenoceptor agonist, CL-316,243 (disodium (R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]propyl]-1,3- benzodioxole-2,2-dicarboxylate). Isoprenaline, salbutamol and salmeterol, but not RO-363 or CL-316,243 produced small, but significant reductions in Evans blue-albumin clearance across unstimulated endothelial monolayers. Inhibition of the response to thrombin by isoprenaline was antagonised by the selective beta 2-adrenoceptor antagonist, ICI-118,551 ((erythro-DL-1(7-methylindan-4- yloxy)3-isopropylaminobutan-2-ol), pKB 8.4). Salmeterol also inhibited hydrogen peroxide-stimulated Evans blue-albumin clearance. Hence, the widely used beta 2-adrenoceptor agonists, salbutamol and salmeterol, are able to reduce endothelial permeability at nanomolar concentrations.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1995

Mutation processes at human minisatellites.

Minisatellites provide one of the most experimentally tractable systems for studying tandem repeat instability in man. Analysis of mutation processes has been greatly aided by the development of single molecule methods for recovering de novo mutants, and of techniques for exploring allele structure in detail. Application of these approaches to man has shown that minisatellites do not primarily mutate by processes such as replication slippage and unequal crossover intrinsic to the tandem repeat array. Instead, germline repeat instability is largely regulated by cis-acting elements near the array and involves unexpectedly complex processes of gene conversion, of potential relevance to the biology of meiosis. These processes can be explored both in humans and, in principle, in transgenic mouse models of human repeat instability.

Alleles↗

PubMed1995

Well-defined genome architecture in the human sperm nucleus.

Using fluorescence in situ hybridization, conventional epifluorescence microscopy, and laser scanning confocal microscopy followed by three-dimensional reconstruction we describe a well-defined higher order packaging of the human genome in the sperm cell nucleus. This was determined by the spatial localization of centromere and telomere regions of all chromosomes and supported by localization of subtelomere sequences of chromosome 3 and the entire chromosome 2. The nuclear architecture in the human sperm is characterized by the clustering of the 23 centromeres into a compact chromocenter positioned well inside the nucleus. The ends of the chromosomes are exposed to the nuclear periphery where both the subtelomere and the telomere sequences of the chromosome arms are joined into dimers. Thus chromosomes in the human sperm nucleus are looped into a hairpin-like configuration. The biological implications of this nuclear architecture in spermatogenesis and male pronuclear formation following fertilization are discussed.

Cell Nucleus↗