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Biomedical subjects

J L Davies

Publications and source records attributed to J L Davies.

At least 19 recordsLinked to original sources

Studies on the interaction of fermentation and microfiltration operations: erythromycin recovery from Saccharopolyspora erythraea fermentation broths.

Changes in fermentation media not only affect the performance of the fermentation itself (with regard to the kinetics of biomass and product formation and the yields obtained) but also the initial product-recovery operations downstream of the fermentor. In this work, microfiltration experiments to remove Saccharopolyspora erythraea biomass from fermentation broth and to recover erythromycin were carried out using two fundamentally different media; a soluble complex medium (SCM) and an oil-based process medium (OBM). Small-scale batch fermentations of 14-L working volume were carried out in triplicate using both media. Broth samples were taken from each fermentation at regular intervals from the end of the exponential-growth phase onwards. These were then processed using a Minitan II (acrylic), tangential crossflow-filtration module, fitted with a single 60 cm(2) Durapore hydrophilic 0.2 microm membrane, operated in concentration mode. The OBM fermentations produced higher titers of erythromycin but required longer fermentation times due to increased lag phases and slower maximum-growth rates. The OBM also increased the loading on the membrane; at maximum product titers residual oil concentrations of 3 g. L(-1), antifoam concentrations of 2 g. L(-1) and flour concentrations estimated at approximately 10 g/L(-1) were typical. It was found that both the permeate flux and erythromycin transmission were affected by the choice of medium. The OBM had significantly lower values for both parameters (12.8 Lm(-2) h(-1) and 89.6% respectively) than the SCM (35.9 Lm(-2) h(-1) and 96.7% respectively) when the fermentations were harvested at maximum erythromycin titers. Transmission of erythromycin stayed approximately constant as a function of fermentation time for both media, however, for the OBM the permeate flux decreased with time which correlated with an increase in broth viscosity. The relatively poor microfiltration performance of the OBM medium was, however, offset by the higher titers of erythromycin that were achieved during the fermentation. The filtration characteristics of the SCM broth did not show any correlation with either broth viscosity or fermentation time. Image-analysis data suggested that there was a correlation between hyphal morphology (main hyphal length) and permeate flux (no such correlation was found for the OBM broth). Moreover, it has been shown for the OBM broth that the residual flour had a profound effect on the microfiltration characteristics. The influence of the residual flour was greater than that imposed by the morphology and concentration of the biomass. The understanding of the factors governing the interaction of the fermentation and microfiltration operations obtained in this work provides a first step towards optimization of the overall process sequence.

Biomass↗

Risk factors for severity of diabetic polyneuropathy: intensive longitudinal assessment of the Rochester Diabetic Neuropathy Study cohort.

OBJECTIVE: Chronic hyperglycemia relates to the occurrence of diabetic polyneuropathy (DPN), but has not yet been shown to relate to its overall severity In addition, the degree and duration of hyperglycemia, which measure of chronic hyperglycemia is most predictive of defined levels of severity of DPN, and which other putative risk factors are involved remain unknown. RESEARCH DESIGN AND METHODS: In a longitudinal study of 264 diabetic individuals in Rochester, MN, risk factors and other diabetic complications assessed at regular intervals during an average of approximately 7 years were tested for their association with a composite score of severity of DPN at the last examination. RESULTS: In multivariate analysis, diabetic retinopathy severity level (at last examination), mean ln(24-h proteinuria x duration of diabetes), and mean GHb were the main covariates for severity of DPN (R2 = 0.33). Excluding markers of microvessel and macrovessel disease, the independent risk factors were mean In(GHb x duration of diabetes), GHb, and type of diabetes (R2 = 0.23). CONCLUSIONS: We found that diabetic microvessel disease, chronic hyperglycemia exposure, and type of diabetes are associated with severity of DPN, and we believe these factors are implicated in its cause. Each of the five markers of microvessel disease was a strong covariate for severity of DPN. Mean GHb predicts severity of DPN better than duration of diabetes, and the latter predicts severity of DPN better than mean fasting plasma glucose. Knowing the severity of microvessel disease, the degree of chronic hyperglycemia exposure, and the type of diabetes provides useful information to evaluate whether a coexisting polyneuropathy and its severity is probably due to diabetes.

Aged↗

No evidence for axonal atrophy in human diabetic polyneuropathy.

In rats with streptozin-induced diabetes mellitus, the caliber of distal myelinated fiber (MF) axons in relation to the number of myelin lamellae is smaller than in controls. This finding usually has been attributed to axonal atrophy, but shrinkage or maldevelopment has also been considered. For human diabetic polyneuropathy (DP), axonal atrophy has been assumed by some investigators, but convincing evidence has not been demonstrated. We morphometrically evaluated transverse sections of 33 sural nerves from carefully evaluated diabetic patients > or = 30 years old without (8 patients) or with (25 patients) DP and compared them with 24 nerves from healthy subjects > or = 30 years old. Nerves from diabetic patients and controls were obtained under identical conditions and processed and evaluated in the same way, using an observer blind to the disease condition. Using computer digitization of electron micrographs, we evaluated the axonal area, perimeter, index of circularity, number of myelin lamellae, and frequency of adaxonal sequestration of 50.4 (mean) +/- 5.8 (SD) MF per sural nerve for healthy subjects and diabetic patients > or = 30 years old. The regression lines of the natural log (In) of axonal area on number of myelin lamellae of diabetic patients (with or without DP) were not significantly different from the regression lines of nerves of healthy subjects for large MFs-the most reliable group in which to recognize atrophy. Likewise, the regression lines of index of circularity (IC) (an index that is decreased with atrophy or shrinkage) on number of myelin lamellae for large fibers was not significantly different between the disease and control groups. The rate of adaxonal sequestration was not significantly higher in DP than in healthy subjects. These results do not support the hypothesis that axonal atrophy occurs in human DP. For small MF, or all MF, some significant differences in regression lines of In axonal area or IC on number of lamellae were found, but these changes are probably explained by events of remyelination and axonal regeneration, which can affect these relationships and are known to occur in DP.

Adult↗

Longitudinal assessment of diabetic polyneuropathy using a composite score in the Rochester Diabetic Neuropathy Study cohort.

Because there are little satisfactory data on change in severity of diabetic polyneuropathy (DP) over time from study of population-based cohorts of diabetic patients in epidemiologic surveys of DP, it is difficult to predict outcome or morbidity or to identify risk factors; it is also difficult to estimate statistical power for use in controlled clinical trials. In this longitudinal study of almost 200 patients from the Rochester Diabetic Neuropathy Study (RDNS) cohort, we assess which symptoms, clinical examinations, tests, or combinations of examinations and tests (composite scores) are best used as minimal criteria for the diagnosis of DP and as a quantitative measure of severity of DP. An abnormality (> or = 97.5th percentile) of a composite score that included the Neuropathy Impairment Score of the lower limbs plus seven tests (NIS(LL)+7 tests), was a better minimal criteria for DP than clinical judgment alone or previously published minimal criteria. First, it provided a more comprehensive assessment of neuropathic impairment. Second, it avoided the overestimated frequency of DP when the minimal criteria for DP was any one or two abnormalities from multiple measurements. Minimal criteria using nerve conduction and reduced heart beat response to deep breathing identified approximately twice as many patients with DP than did clinical examination and vibration detection threshold using CASE IV. This difference could be used to subclassify state 1 DP. Although various individual measures of DP, for example, vibration detection threshold (as evaluated by CASE IV and the 4, 2, and 1 stepping algorithm [see text]), were good measures of worsening, the composite score NIS(LL)+7 tests (assessing neuropathic impairment) was much better at showing monotone worsening. Using this composite score, the average diabetic patient in the RDNS worsened by 0.34 points per year, whereas patients with diabetic polyneuropathy worsened by 0.85 points per year. On the assumption that a therapeutic agent may prevent worsening of DP but not cause improvement, controlled clinical trials of patients with DP would need to be conducted for a period of 3 years to achieve a meaningful change of 2 NIS points (the level of abnormality considered by a Peripheral Nerve Society consensus group to be clinically meaningful).

Adult↗

Mixed cavernous and capillary intraosseous hemangioma of the foot.

Hemangiomas of bone are rare lesions accounting for approximately 1% of all primary bone tumors. Intraosseous hemangiomas of the foot are especially rare, with only sparse reports in the literature. Presented here is a case study of an erosive bony lesion of the midfoot that was microscopically and histopathologically proven to be a mixed cavernous and capillary hemangioma. Eradication of the lesion during diagnostic biopsy obviated further treatment.

Bone Neoplasms↗

Behaviour disorder in an adolescent with terminal deletion of chromosome 3.

Individuals with terminal deletion of the long arm of chromosome 3 are rare and survival into adulthood has not been previously reported. A 15-year-old with this condition was studied and the difficulties in management of the manifest behaviours are described. This chromosomal abnormality may be associated with mental and functional deterioration as well as severe self-injurious behaviour, commencing in early childhood.

Activities of Daily Living↗

Saturation multipoint linkage mapping of chromosome 6q in type 1 diabetes.

Linkage analysis of type 1 diabetes sib pair families (n = 334) has suggested two separate regions of human chromosome 6q are linked to disease (designated IDDM5 and IDDM8). To test if these are false positive results, all available sib pair families (n = 429) were typed using a 92% informative map of chromosome 6q and multipoint analysis. The two regions still showed positive evidence of linkage, most notably the proterminal region, 6q27, corresponding to IDDM8 (MLS = 2.57, p = 0.0006; lambda s = 1.17). In addition, some evidence of transmission disequilibrium was seen with marker a046xa9 (IDDM5).

Chromosome Mapping↗

Retrospective review of endoscopic plantar fasciotomy--1992 through 1994.

Endoscopic plantar fasciotomy is a rewarding procedure for both patient and surgeon. A vast majority of the patients have complete or near-complete resolution of heel pain at 6 months postoperatively. The procedure, however, is not without side effects and complications. This retrospective statistical study describes the postoperative side effects and complications of endoscopic plantar fasciotomy from 1992 to 1994. The procedure has been modified in an attempt to reduce several of the more commonly reported side effects.

Endoscopy↗

Analysis of the CD3 gene region and type 1 diabetes: application of fluorescence-based technology to linkage disequilibrium mapping.

The CD3 gene region on chromosome 11q23 has been implicated in susceptibility to type 1 (insulin-dependent) diabetes mellitus. Using semi-automated fluorescence-based technology, we have undertaken association and linkage analysis of a dinucleotide microsatellite in the CD3 delta (CD3D) gene. We have also performed a large case-control analysis of a restriction fragment length polymorphism (RFLP) in the CD3 epsilon (CD3E) gene, 26 kb from CD3D. We found no evidence for the previously reported association between the 8 kb allele of the RFLP and disease in a UK dataset of 403 diabetic patients and 446 nondiabetic controls. Furthermore, the use of the transmission/disequilibrium test (TDT) showed no evidence of linkage or association to type 1 diabetes at either marker locus. We conclude that the CD3 gene region does not contribute significantly to IDDM susceptibility. We have successfully applied semi-automated, fluorescence-based technology to undertake association analysis on the CD3D microsatellite. Moreover, by analysing 94 other dinucleotide repeat markers, we conclude that fluorescence-based methodology can generally be applied to large-scale, semi-automated association studies with most microsatellite markers.

Adolescent↗

A genome-wide search for human type 1 diabetes susceptibility genes.

We have searched the human genome for genes that predispose to type 1 (insulin-dependent) diabetes mellitus using semi-automated fluorescence-based technology and linkage analysis. In addition to IDDM1 (in the major histocompatibility complex on chromosome 6p21) and IDDM2 (in the insulin gene region on chromosome 11p15), eighteen different chromosome regions showed some positive evidence of linkage to disease. Linkages to chromosomes 11q (IDDM4) and 6q (IDDM5) were confirmed by replication, and chromosome 18 may encode a fifth disease locus. There are probably no genes with large effects aside from IDDM1. Therefore polygenic inheritance is indicated, with a major locus at the major histocompatibility complex.

Adolescent↗

Chromosome-specific microsatellite sets for fluorescence-based, semi-automated genome mapping.

To facilitate large-scale genetic mapping of the human genome, we have developed chromosome-specific sets of microsatellite marker loci suitable for use with a fluorescence-based automated DNA fragment analyser. We present 254 dinucleotide repeat marker loci (80% from the Généthon genetic linkage map) arranged into 39 sets, covering all 22 autosomes and the X chromosome. The average distance between adjacent markers is 13 centiMorgans, and less than 4% of the genome lies more than 20 cM from the nearest marker. Each set of microsatellites consists of up to nine marker loci, with allele size ranges that do not overlap. We selected marker loci on the basis of their reliability in the polymerase chain reaction, polymorphism content, map position and the accuracy with which alleles can be scored automatically by the Genotyper program.

Automation↗

Differences in the perceptions of HIV risk amongst dental care providers in Western Australian clinics.

This paper examines the perceived risk of occupationally contracting HIV among dental care providers. This examination is based upon responses to a mailed questionnaire from all registered dentists (76 per cent response rate, n = 550) and dental therapists (63 per cent response rate, n = 208) in Western Australia during 1992. Results indicate that: 1) dental care providers who perceive a high risk of occupationally contracting HIV report a more conservative, cautious approach to HIV infection than do providers who perceive less risk of contracting the virus; 2) dental therapists are more likely than dentists to report a higher degree of perceived risk of occupationally contracting HIV; and 3) dentists are more likely than dental therapists to perceive compliance with universal precaution guidelines in dental practices in which they work. Reasons are presented for a suspicion that both sets of perceptions may be exaggerated. The need to educate dental therapists on the realistic risks of occupationally contracting HIV and to educate dentists on the value of compliance (and of appearing to comply) with universal precaution guidelines in order to help reduce undue stress and hindrances in the provision of safe and effective dental care in this era of AIDS concludes this paper.

Acquired Immunodeficiency Syndrome↗

Increase of plasma IL-6 concentration with age in healthy subjects.

The present study demonstrated that plasma IL-6 concentration was higher in older subjects than in younger ones and significantly in the male group (P = 0.02); Spearman rank correlation showed that plasma IL-6 concentration was positively correlated with age (r = 0.28, N = 55, P < 0.05); there was a highly significant correlation between the concentrations in plasma IL-6 and IL-1 alpha (r = 0.51, N = 52, P < 0.001). These findings suggest the possibility that age-related changes of plasma IL-6 and IL-1 alpha may provide a pathological basis for the susceptibility to such illness as commonly occurs in elderly people, especially Alzheimer's disease as the two interleukins can induce the production of alpha 1-antichymotrypsin and beta-amyloid protein precursor.

Adult↗

Transcendental meditation, mindfulness, and longevity: an experimental study with the elderly.

Can direct change in state of consciousness through specific mental techniques extend human life and reverse age-related declines? To address this question, 73 residents of 8 homes for the elderly (mean age = 81 years) were randomly assigned among no treatment and 3 treatments highly similar in external structure and expectations: the Transcendental Meditation (TM) program, mindfulness training (MF) in active distinction making, or a relaxation (low mindfulness) program. A planned comparison indicated that the "restful alert" TM group improved most, followed by MF, in contrast to relaxation and no-treatment groups, on paired associate learning; 2 measures of cognitive flexibility; mental health; systolic blood pressure; and ratings of behavioral flexibility, aging, and treatment efficacy. The MF group improved most, followed by TM, on perceived control and word fluency. After 3 years, survival rate was 100% for TM and 87.5% for MF in contrast to lower rates for other groups.

Adaptation, Psychological↗

Respiratory teaching of patients: how effective is it?

In order to evaluate the effectiveness of a structured respiratory teaching programme, clients with chronic obstructive pulmonary disease who were hospitalized in a 13-month period both prior to and following the implementation of the programme were compared on several parameters to assess changes in their ability to manage their disabilities. The study demonstrated that clients who participated in the teaching sessions had fewer hospital admissions, shorter lengths of hospital stay, and longer stays in the community. A sub-group of clients who were or had been in at-risk occupations was identified as representing the 'revolving door' client with shorter hospital and community stays. The teaching programme is described as well as specific elements that can be used for a shorter teaching experience to respond to time constraints when necessary.

Adult↗