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Biomedical subjects

A L Allen

Publications and source records attributed to A L Allen.

At least 19 recordsLinked to original sources
PubMed2001

Direct incorporation of glucosamine and N-acetylglucosamine into exopolymers by Gluconacetobacter xylinus (=Acetobacter xylinum) ATCC 10245: production of chitosan-cellulose and chitin-cellulose exopolymers.

Gluconacetobacter xylinus (=Acetobacter xylinum) ATCC 10245 incorporated 2-amino-2-deoxy-D-glucose (glucosamine) and 2-acetamido-2-deoxy-D-glucose (N-acetylglucosamine), but not 3-O-methyl-D-glucose or 2-deoxy-D-glucose into exopolymers. Incorporation was confirmed by gas chromatography with and without mass spectrometry, Fourier transform infrared, and 1H nuclear magnetic resonance. The average molar percentage of glucosamine and N-acetylglucosamine in the exopolymers was about 18%.

Acetylglucosamine↗
PubMed2001

Management of warts and molluscum in adolescents.

Warts continue to be a therapeutic challenge, especially when they are numerous or widespread; in contrast, treatment of molluscum is comparatively more successful. A single, most effective treatment for either infection has not been defined. Conventional methods attempt to non-specifically destroy infected tissue. Most of these procedures are painful and require multiple treatments or compliance with daily application of a medication. The efficacy of destructive techniques has not been verified in placebo-controlled clinical trials and success rates reported in uncontrolled studies are difficult to interpret and often no better than that those achieved with a placebo. Alternative pharmacological approaches are aimed at stimulating immunologic or antiviral responses. Further study is needed to establish efficacy of these treatments.

Adolescent↗
PubMed2000

Timing the radiations of leaf beetles: hispines on gingers from latest cretaceous to recent.

Stereotyped feeding damage attributable solely to rolled-leaf hispine beetles is documented on latest Cretaceous and early Eocene ginger leaves from North Dakota and Wyoming. Hispine beetles (6000 extant species) therefore evolved at least 20 million years earlier than suggested by insect body fossils, and their specialized associations with gingers and ginger relatives are ancient and phylogenetically conservative. The latest Cretaceous presence of these relatively derived members of the hyperdiverse leaf-beetle clade (Chrysomelidae, more than 38,000 species) implies that many of the adaptive radiations that account for the present diversity of leaf beetles occurred during the Late Cretaceous, contemporaneously with the ongoing rapid evolution of their angiosperm hosts.

Animals↗
PubMed2000

What's new in human papillomavirus infection.

Warts continue to be a therapeutic challenge, especially widespread warts on children. A single, most effective treatment has not been defined. Conventional methods attempt to nonspecifically destroy infected tissue. Most of these procedures are painful, poorly tolerated by children, and often require multiple treatments. The efficacy of destructive techniques is impossible to verify in controlled clinical trials. Uncontrolled success rates are suboptimal and often no better than that seen with placebos. Alternative pharmacologic approaches have been designed to stimulate immunologic responses or provide anti-viral activity. Further study is needed to establish efficacy of these treatments.

Adjuvants, Immunologic↗
PubMed2000

An evaluation of chemical arthrodesis of the proximal interphalangeal joint in the horse by using monoiodoacetate.

The use of monoiodoacetate (MIA) for arthrodesis of the proximal interphalangeal joint (PIJ) and the effect of exercise on the degree of fusion were investigated. Eight horses received 3 injections (Weeks 0, 3, 6) of MIA (2 mL; 60 mg/mL) into the right or left front PIJ. Peri-operatively, the horses received phenylbutazone, butorphanol, and abaxial sesamoidean nerve blocks to relieve pain. During the study, the horses were monitored for general health, lameness, and swelling around the injection area. Radiographs were taken biweekly to evaluate bony fusion. Horses were randomly divided into non-exercised and exercised groups. Exercise consisted of 20 minutes of trotting on a treadmill (4 m/s), 3 days per week for 13 weeks. The horses were euthanized at 24 weeks. Slab sections of the PIJ were evaluated grossly and radiographically for bony fusion. Histologic examinations were performed to evaluate articular cartilage. Three horses were excluded from the study after developing soft tissue necrosis around the injection site, septic arthritis, and necrotic tendinitis. The remaining horses remained healthy, developed a grade 1 to 4 lameness with minimal to severe swelling in the PIJ region. All 5 horses showed radiographic evidence of bony fusion, however, no fusion was present when injected joints were examined on postmortem examination. Histologic examination revealed thinning of the cartilage, diffuse necrosis of chondrocytes, with the calcified zone intact. Subjectively, exercise did not influence the degree of cartilage destruction. Based on this study, chemical arthrodesis cannot be advocated in clinical cases because of the high complication rate and lack of bony fusion.

Animals↗
PubMed1999

The use of postmortem radiography as an aid in diagnosing, documenting, and understanding disease in animals.

Postmortem radiography can be a valuable supplement to traditional necropsy. This article provides examples where postmortem radiographs have been useful in diagnosing and documenting lesions in animals, and have helped demonstrate important principles of the pathology and the pathogenesis of lesions identified at necropsy. This article also discusses additional circumstances where the application of postmortem radiography might be worthwhile.

Animal Diseases↗
PubMed1999

Biosynthesis of novel exopolymers by Aureobasidium pullulans.

Aureobasidium pullulans ATCC 42023 was cultured under aerobic conditions with glucose, mannose, and glucose analogs as energy sources. The exopolymer extracts produced under these conditions were composed of glucose and mannose. The molar ratio of glucose to mannose in the exopolymer extract and the molecular weight of the exopolymer varied depending on the energy source and culture time. The glucose content of exopolymer extracts formed with glucose and mannose as the carbon sources was between 91 and 87%. The molecular weight decreased from 3.5 x 10(6) to 2.12 x 10(6) to 0.85 x 10(6) to 0.77 x 10(6) with culture time. As the culture time increased, the glucose content of the exopolymer extract formed with glucosamine decreased from 55 +/- 3 to 29 +/- 2 mol%, and the molecular weight increased from 2.73 x 10(6) to 4.86 x 10(6). There was no evidence that glucosamine was directly incorporated into exopolymers. The molar ratios of glucose to mannose in exopolymer extracts ranged from 87 +/- 3:13 +/- 3 to 28 +/- 2:72 +/- 2 and were affected by the energy source added. On the basis of the results of an enzyme hydrolysis analysis of the exopolymer extracts and the compositional changes observed, mannose (a repeating unit) was substituted for glucose, which gave rise to a new family of exopolymer analogs.

3-O-Methylglucose↗
PubMed1998

The natural history of condyloma in children.

BACKGROUND: Condyloma acuminatum, an infection caused by human papillomavirus (HPV), has become one of the most common sexually transmitted diseases. Correspondingly, anogenital warts are more frequently diagnosed in children. Twenty-five years ago a landmark prospective study showed that untreated common cutaneous warts in children spontaneously regress within 2 years in two thirds of cases, but a similar study of condyloma has not been published. Several treatment options are available for condyloma in adults; none have been studied or approved by the US Food and Drug Administration for treatment of children. OBJECTIVE: Our purpose was to review a cohort of children with condyloma to determine the natural history. METHODS: Of 75 originally identified subjects with condyloma, 41 qualified for further retrospective or prospective evaluation, including distribution of lesions, duration of disease, gender, and treatment, if any. RESULTS: Overall, condylomas in 31 of 41 children (76%) experienced resolution. Spontaneous resolution occurred within 5 years in 22 of 41 subjects (54%), including 6 of 8 (75%) who never received treatment, and 16 of 33 (49%) in whom treatment failed. In 9 of 33 treated children (27%), resolution occurred during treatment. Girls presented three times more often than boys and resolution occurred comparatively more often in girls. CONCLUSION: Spontaneous resolution of pediatric condyloma occurred in more than half of our subjects. Nonintervention is a reasonable initial approach to managing venereal warts in children.

Age Distribution↗
PubMed1998

The effects of partial thyroidectomy on the development of the equine fetus.

A syndrome of congenital hypothyroidism and dysmaturity has been an important cause of reproductive loss and foal mortality in western Canada. The cause and pathogenesis of this syndrome is under investigation. One issue to be addressed is whether all the anomalies present in affected foals are produced concurrently by the same agent, or if affected foals are primarily hypothyroid in utero which induces the associated lesions. This study was designed to document the effects of fetal thyroidectomy, at about 215 days of gestation, on the growth and development of the equine fetus and to compare the anomalies present to those reported in the spontaneously occurring syndrome of foals in western Canada. Two sham-operated controls and 4 partially thyroidectomised foals were carried to term following surgery. Sham-operated control foals were normally developed. Partially thyroidectomised foals were hypothyroid; had hyperplastic thyroid gland remnants; abnormal behaviour and locomotor skills; and numerous, marked deficiencies in their skeletal development. The anomalies present in partially thyroidectomised foals were comparable to those reported in congenitally hypothyroid neonates of other species, including human infants, and were similar to those described in congenitally hypothyroid and dysmature foals reported in western Canada.

Animals↗
PubMed1997

Incorporation of 2-hydroxyl fatty acids by Acinetobacter calcoaceticus RAG-1 to tailor emulsan structure.

Acinetobacter calcoaceticus RAG-1 was cultured on different chain length saturated 2-hydroxyl fatty acid (2-HOFA) carbon sources as follows: C12:0 (2-OH), C14:0 (2-OH), C16:0 (2-OH) and C18:0 (2-OH). These 2-HOFAs were used as either sole carbon sources or cosubstrates with C14:0 (total 1% w/v) to form new emulsans (EMs) having controlled side chain FA structure and, therefore, unique emulsifier characteristics. EM yields and cell dry weights ranged from 0.6 to 1.8 g/l and 0.9 to 3.9 g/l, respectively, depending on the carbon source(s) and the cultivation conditions. The content of C12:0 (2-OH) EM substituents reached high levels (306 nmol/mg-EM, 64.4 mol% of total FAs) by selectively feeding this FA. Substantial quantities of 2-HOFAs with chain lengths > or = C14-up to 96 nmo1/mg-EM or 15.2 mol% for C16:0 (2-OH)-were also incorporated in EMs by providing the corresponding 2-HOFA carbon source in the medium. By increasing the medium 2-HOFA concentration large increases in EM total FA contents resulted. The EM FA content was as high as 955 nmol/mg-EM or 23 wt% for a culture containing 0.75 g/100 ml C18:0 (2-OH). An important metabolic pathway involved in EM side chain formation from C16:0 (2-OH) and C18:0 (2-OH) involves decarboxylation, oxidation of the alkanol to the corresponding n-1 FA-CoA intermediate and formation of odd chain length substituent side chain linkages by an EM acyl transferase. Addition of the enzyme alkylating agent iodoacetamide to cultures was used to: (i) enhance the incorporation into EMs of both C12:0 (2-OH) and C16:0 (2-OH) substituents; and (ii) increase by 1.3 to 1.8 fold (by wt.) the total EM FA content. Finally, it was concluded that enhanced emulsification activity of EMs is not necessarily achieved by forming products with relatively high 2- and 3-hydroxydodecanoic acid contents.

Acinetobacter calcoaceticus↗
PubMed1997

Bioengineering of emulsifier structure: emulsan analogs.

Strategies were investigated to modulate the side chain structure of emulsans formed by Acinetobacter calcoaceticus RAG-1. Analysis of emulsan fatty acid side chain groups by gas chromatography--mass spectrometry (GC-MS) revealed that by provoking the exogenous n-alkanoic fatty acids 15:0, 16:0, and 17:0, emulsan analogs were formed with 53, 46, and 44 mol%, respectively, of fatty acid substituents with chain lengths equal to that of the carbon source. In contrast, the increase in emulsan fatty acids of chain lengths less than 15 or greater than 17 by providing corresponding shorter and longer chain length fatty acids as carbon sources was not substantial. When [1-13C]-labeled (99% enriched) palmitic acid was used as a carbon source along with acetate, analysis of M/z 75/74 and 87/88 isotopomer ratios by GC-MS indicated that 84 and 86% of the 16:0 (9-cis) side groups, respectively, were incorporated intact from the 16:0 carbon source. The percentage of 14- 15-, 16-, 17-, and 18-carbon chain length fatty acid esters that were monounsaturated were 11, 26, 50, 70, and 85% respectively. Based on the observed percentage of unsaturated chain length dependence and almost identical enrichment at C-1 of 16:0 and 16:1 (9-cis) side groups from [1-13 C]-labeled experiments, it was concluded that desaturation of preformed n-alkanoic acids was the predominant mechanism of their formation. Further work established correlations between side chain structure and product emulsification specificity/activity, so that bioengineered emulsans with improved selectivity can now be formed.

Acinetobacter calcoaceticus↗
PubMed1996

Aortic and iliac artery thrombosis in calves: nine cases (1974-1993).

OBJECTIVE: To identify common clinical and diagnostic features of calves with aortic or iliac artery thrombosis that might aid in antemortem diagnosis of this condition. DESIGN: Retrospective case series. ANIMALS: 9 calves < or = 6 months old in which aortic or iliac artery thrombosis was confirmed at necropsy. RESULTS: All calves had an acute onset of paresis or flaccid paralysis of 1 or both hind limbs. Affected limbs were hypothermic and had diminished spinal reflexes and diminished pulse pressures. Diagnosis was definitively established in 2 calves by use of angiography. All 9 calves died or were euthanatized. CLINICAL IMPLICATIONS: This condition is rare and could be mistaken for more common diseases of young cattle, such as traumatic injury of the axial or appendicular skeleton, vertebral osteomyelitis, nutritional muscular dystrophy associated with vitamin E or selenium deficiency, injury to the sciatic or femoral nerves, or clostridial myositis.

Animals↗