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Biomedical subjects

G Hammond

Publications and source records attributed to G Hammond.

At least 19 recordsLinked to original sources
PubMed2006

Isospin symmetry of odd-odd mirror nuclei: identification of excited states in N=Z-2 48Mn.

Excited states have been observed in the N=Z-2 odd-odd nucleus 48Mn for the first time. Through comparison with the structure of 48V, a first high-spin study of an odd-odd mirror pair has been achieved. Differences between the T=1 analogue states in this pair have been interpreted in terms of Coulomb effects, with the aid of shell-model calculations in the full pf valence space. Unlike other mirror pairs, the energy differences have been interpreted almost entirely as due to a monopole effect associated with smooth changes in radius (or deformation) as a function of angular momentum. In addition, the large energy shift between analogue negative-parity states is interpreted in terms of the electromagnetic spin-orbit interaction in nuclei.

Journal Article↗
PubMed2006

Comparison of ultrasonography, radiography and a single computed tomography slice for fluid identification within the feline tympanic bulla.

Evaluation of the tympanic bulla (TB) in cases of acute feline otitis media can be a diagnostic challenge, although a feature often associated with this condition is the accumulation of fluid or material within the middle ear cavity. A technique is reported allowing optimum imaging of the feline TB using ultrasound (US) and recording of the appearance of gas and fluid-filled TB. A random number of bullae in 42 feline cadavers were filled with lubricant and rostroventral-caudodorsal oblique radiographs, single slice computed tomography (CT) images and US images were created and interpreted by blinded operators. The content (fluid or gas) of each TB was determined using each technique and the cadavers were then frozen and sectioned for confirmation. CT remained the most accurate diagnostic method, but US produced better results than radiology. Given the advantages of US over other imaging techniques, these results suggest that further work is warranted to determine applications of this modality in the evaluation of clinical cases of feline otitis media.

Animals↗
PubMed2006

Use of reconstructed computed tomography for the assessment of joint spaces in the canine elbow.

OBJECTIVES: To assess the accuracy of reconstructed computed tomography for imaging canine elbow joint spaces. METHODS: Computed tomography scans of eight cadaveric elbows were obtained and reconstructed computed tomography images were formatted in the dorsal and sagittal planes. Humeroradial and humeroulnar joint space measurements were obtained from these images. Intra-observer and inter-observer variations in joint space measurements were assessed, as was the effect of specimen positioning (inter-image variation). After freezing, four elbows were sectioned in the dorsal plane and four in the sagittal plane. In addition to visual comparison of the frozen sections with reconstructed computed tomography images, joint space measurements were obtained from frozen sections and compared with those from reconstructed computed tomography images. Variation was assessed using statistical calculations and graphical techniques. RESULTS: Both inter-image and intra-observer analyses revealed good agreement and low variation between data sets. Inter-observer correlation was only moderate, though variation was low. Visually, the reconstructed computed tomography images accurately reflected the frozen section anatomy. Agreement between frozen section and reconstructed computed tomography joint space measurements was good, with minimal variation. CLINICAL SIGNIFICANCE: These results indicate that reconstructed computed tomography is capable of accurately imaging elbow joint spaces and precise joint space measurements can be obtained. Reconstructed computed tomography may be useful for determining joint space measurements and detecting elbow incongruencies in dogs with elbow dysplasia.

Animals↗
PubMed2005

Handedness in schizophrenia: a quantitative review of evidence.

OBJECTIVE: The prevalence of various anomalous handedness subtypes in schizophrenia patients remains ambiguous. Although current literature favours the notion that the shift in lateral preferences seen is because of an increase of mixed-handedness, several studies suggest that exclusive left handedness is more prevalent than in the general population. METHOD: Over 40 studies with reported prevalence data on various handedness subtypes in a schizophrenia population were evaluated by meta-analysis. Combined odds ratios for the three common handedness subtypes (left, mixed, and right) were separately calculated. RESULTS: Each of the three atypical hand dominance patterns were significantly greater in schizophrenia patients than in control subjects, showing that the leftward shift in handedness distribution is not entirely because of an increase in mixed-handedness alone. CONCLUSION: An increase of exclusive left-handedness is at variance with the prevailing assertion that the handedness shift in schizophrenia patients is because of a diffuse and bilateral hemispheric insult.

Functional Laterality↗
PubMed2004

Effective charges in the fp shell.

Following the heavy-ion fusion-evaporation reaction 32S+24Mg at 95 MeV beam energy the lifetimes of analogue states in the T(z)=+/-1/2 A=51 mirror nuclei 51Fe and 51Mn have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p) approximately 1.15e and epsilon(n) approximately 0.80e.

Journal Article↗
PubMed2004

Nuclear phosphoinositides and their functions.

Phosphoinositides are minor components of biological membranes, which have emerged as essential regulators of a variety of cellular processes, both on the plasma membrane and on several intracellular organelles. The versatility of these lipids stems from their ability to function either as substrates for the generation of second messengers, as membrane-anchoring sites for cytosolic proteins or as regulators of the actin cytoskeleton. Despite a vast literature demonstrating the presence of phosphoinositides in the nucleus, only recently has the function(s) of the nuclear pool of these lipids and their soluble analogues, inositol polyphosphates, started to emerge. These compounds have been shown to serve as essential co-factors for several nuclear processes, including DNA repair, transcription regulation and RNA dynamics. In this light, phosphoinositides and inositol polyphosphates might represent high turnover activity switches for nuclear complexes responsible for these processes. The regulation of these large machineries would be linked to the phosphorylation state of the inositol ring and limited temporally and spatially based on the synthesis and degradation of these molecules.

Active Transport, Cell Nucleus↗
PubMed2004

Using fragment chemistry data mining and probabilistic neural networks in screening chemicals for acute toxicity to the fathead minnow.

The paper is illustrating how the general data mining methodology may be adapted to provide solutions to the problem of high throughput virtual screening of organic chemicals for possible acute toxicity to the fathead minnow fish. The present approach involves mining fragment information from chemical structures and is using probabilistic neural networks to model the relationship between structure and toxicity. Probabilistic neural networks implement a special class of multivariate non-linear Bayesian statistical models. The mathematical principles supporting their use for value prediction purposes are clarified and their peculiarities discussed. As part of the research phase of the data mining process, a dataset consisting of 800 structures and associated fathead minnow (Pimephales promelas) 96-h LC50 acute toxicity endpoint information is used for both the purpose of identifying an advantageous combination of fragment descriptors and for training the neural networks. As a result, two powerful models are generated. Model 1 implements the basic PNN with Gaussian kernel (statistical corrections included) while Model 2 implements the PNN with Gaussian kernel and separated variables. External validation is performed using a separate dataset consisting of 86 structures and associated toxicity information. Both learning and generalization capabilities of the two models are investigated and their limitations discussed.

Animals↗
PubMed2004

Effects of galantamine in patients with mild Alzheimer's disease.

BACKGROUND: Galantamine is an acetylcholinesterase inhibitor that modulates nicotinic receptors. It is effective in mild to moderate Alzheimer's disease (AD) but no trial has focused exclusively on mild AD. We performed a post-hoc sub-set analysis using data from four randomised trials to explore the efficacy of galantamine versus placebo in mild AD. METHODS: Participants in all studies met NINCDS-ADRDA criteria for probable AD. We examined data from patients with baseline Mini Mental State Examination (MMSE) 21-24 who received galantamine 24 mg/day (GAL) or placebo (PLAC). Scores for the Alzheimer's Disease Assessment Scale-cognitive subset (ADAS-cog), Clinician's Interview-Based Impression of Change (CIBIC), Disability Assessment for Dementia (DAD), and ACDS-ADL scales were compared. RESULTS: Of the 694 patients (362 GAL, 332 PLAC, mean baseline MMSE 22.4 +/- 1.1, mean age 74 +/- 7.9 years), 65% completed 6 months treatment (223 GAL, 229 PLAC). Mean change in ADAS-cog at 6 months was -1.5 (95% confidence interval -2.2, -0.8, p < 0.001) for GAL and +0.2 (-0.6, 0.9, p = 0.72) for PLAC. This difference was statistically significant (p = 0.001). Significantly more patients receiving galantamine were classified as 'improved' using the CIBIC (26.9% GAL vs 14.3% PLAC, p < 0.001). Galantamine was generally well tolerated; most common adverse events were nausea, vomiting and diarrhoea. CONCLUSIONS: Pooled data from four randomised trials of patients with mild AD indicate that patients who received galantamine 24 mg/day for 6 months improved cognition more often than those who received placebo and that a higher proportion receiving galantamine were globally improved. This suggests that patients with mild AD benefit from galantamine treatment.

Aged↗
PubMed2002

The association of breast mitogens with mammographic densities.

Radiologically dense breast tissue (mammographic density) is strongly associated with risk of breast cancer, but the biological basis for this association is unknown. In this study we have examined the association of circulating levels of hormones and growth factors with mammographic density. A total of 382 subjects, 193 premenopausal and 189 postmenopausal, without previous breast cancer or current hormone use, were selected in each of five categories of breast density from mammography units. Risk factor information, anthropometric measures, and blood samples were obtained, and oestradiol, progesterone, sex hormone binding globulin, growth hormone, insulin-like growth factor-I and its principal binding protein, and prolactin measured. Mammograms were digitised and measured using a computer-assisted method. After adjustment for other risk factors, we found in premenopausal women that serum insulin-like growth factor-I levels, and in postmenopausal women, serum levels of prolactin, were both significantly and positively associated with per cent density. Total oestradiol and progesterone levels were unrelated to per cent density in both groups. In postmenopausal women, free oestradiol (negatively), and sex hormone binding globulin (positively), were significantly related to per cent density. These data show an association between blood levels of breast mitogens and mammographic density, and suggest a biological basis for the associated risk of breast cancer.

Adult↗
PubMed2001

Modification of the human blink reflex by transient and sustained features of acoustic prestimulation.

The effects of acoustic stimuli whose onsets and durations were controlled to vary their transient and sustained features on the size of a subsequently elicited blink reflex were examined in humans. Prestimuli both with and without transient features inhibited the reflex when they preceded the eliciting stimulus by brief lead intervals, showing that acoustic transients are sufficient, but not necessary, for reflex inhibition. Inhibition evoked by transient and sustained stimulus features showed partial summation, and inhibition evoked by stimuli with only transient and with transient and sustained features showed similar decay functions with increasing lead intervals. Blink augmentation was found at longer lead intervals early but not late in a session, and was more evident in women than men. Prestimuli with only transient features were more effective than those with both transient and sustained features, showing that sustained stimulus energy at the time of reflex elicitation is not only not necessary for blink augmentation, but also diminishes it.

Acoustic Stimulation↗
PubMed2001

Effect of lateralized gaps in noise on the cutaneous blink reflex in humans.

The early (R1) and late (R2) components of the cutaneous blink reflex in right-handed humans were recorded in three experiments to examine the lateral symmetry of a simple excitatory process in their brainstem pathways and of the control of the excitability of the pathways by gaps in acoustic noise. Experiment 1 showed that a stimulus below R1-elicitation threshold increased the excitability of the right R1 pathway more than the left but that the rate of decay was similar on both sides. Experiment 2 showed that a brief unilateral gap in noise affected the R1 and R2 reflex pathways bilaterally. Experiment 3 showed that R2 varied with gap duration and that gaps to the left and right ears had indistinguishable effects. The finer temporal resolution of events in the right sensory field of right-handers seen in psychophysical judgments is not seen in the descending control of brainstem excitability.

Acoustic Stimulation↗
PubMed1998

Co-registration of cortical magnetic stimulation and functional magnetic resonance imaging.

Functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) are noninvasive techniques recently used to investigate cortical motor physiology. However, these modalities measure different phenomena, and in studies of human motor control they have given inconsistent results. We have developed a reproducible technique which co-registers TMS and fMRI, using a frameless method. In four normal subjects, the TMS map and fMRI activation were present on the primary motor cortex contralateral to the target hand, with some extension into primary sensory cortex. fMRI activation alone was also present in the medial motor cortex bilaterally and in the sensorimotor cortex ipsilateral to the target hand. This technique allows a more comprehensive evaluation of the physiologic events involved in motor control.

Adult↗
PubMed1998

Long-term follow-up of rheumatic patients undergoing left-sided valve replacement with tricuspid annuloplasty--validity of preoperative echocardiographic criteria in the decision to perform tricuspid annuloplasty.

Between September 1989 and December 1991, modified De Vega tricuspid annuloplasty was performed in 43 patients who survived surgery for mitral or mitral plus aortic valve replacement. The preoperative indications for tricuspid annuloplasty were moderate to severe tricuspid regurgitation (TR) in 33 patients and mild or no TR but with a dilated tricuspid annulus (> or =30 mm) as measured by 2-dimensional echocardiography at end-diastole in 10 patients. The mean age was 31 +/- 13 years. The mean duration of follow-up was 57 +/- 18 months. Overall long-term mortality was 12%. On Doppler color flow mapping, postoperative severe TR was present in 1 patient and moderate TR in 4 patients at latest follow-up. The tricuspid annulus diameter decreased from 37 +/- 5 mm preoperatively to 24 +/- 6 mm at latest follow-up. During the study period, an additional 77 patients underwent mitral valve replacement or double valve replacement, but without tricuspid annuloplasty. Within this group, 38 patients had a preoperative tricuspid annulus diameter of > or =30 mm, and 5 of these patients (13%) developed moderate or severe TR in the postoperative period, which may have been prevented had clinicians adhered to the preoperative indications for tricuspid annuloplasty. Thus, preoperative echocardiographically documented moderate or severe TR or a tricuspid annulus diameter of > or =30 mm are valid indications for performing tricuspid annuloplasty; modified De Vega tricuspid annuloplasty is a durable procedure in rheumatic patients; it appears that reducing the diastolic tricuspid annulus diameter to 24 mm is adequate to prevent residual TR in the long term.

Adult↗
PubMed1998

Comparative evaluation of chlamydiazyme, PACE 2, and AMP-CT assays for detection of Chlamydia trachomatis in endocervical specimens.

We conducted a comparative evaluation of the Chlamydiazyme (Abbott Laboratories), PACE 2 (Gen-Probe), and AMP-CT (Gen-Probe) assays for the detection of Chlamydia trachomatis in endocervical samples. Specimens from 787 females were included in the study. The sensitivities of the PACE 2 and Chlamydiazyme assays in comparison to the results of the AMP-CT assay were 79.3 and 63.4%, respectively. The specificities of the Chlamydiazyme and PACE 2 assays were 100%. All of the positive specimens detected in this study were positive by the AMP-CT assay. On the basis of the final results of the comparison, the prevalence of C. trachomatis in the population was 10.4%. Retesting of specimens whose results were in the intermediate zone by the PACE 2 assay by a probe competition assay identified some additional true-positive specimens. Amplification assay testing of such specimens did not significantly increase the yield. The majority of specimens which tested positive by the AMP-CT assay only were not in the intermediate zone by the PACE 2 assay. We were unable to identify demographic or clinical factors which could predict those individuals who tested positive by amplified tests but not by nonamplified tests. The Gen-Probe PACE 2 assay proved to be superior to the Chlamydiazyme assay for the screening and diagnosis of C. trachomatis infections in female endocervical specimens.

Adult↗
PubMed1997

Risk factors for the development of non-response to first-line treatment for tuberculosis in southern Vietnam.

BACKGROUND: Acquired resistance to standard chemotherapy for tuberculosis (TB) is an increasing problem worldwide. Vietnam has one of the highest incidences of TB and also has a large population of potential migrants to other countries. Since 1979 the International Organisation for Migration (IOM) has been running a supervised programme of TB treatment for intending migrants from Vietnam where few facilities for bacteriological culture and sensitivity testing exist. This study aimed to assess the most important factors for predicting non-response to first-line treatment as treatment starts and whether any further indicators occur during the course of treatment which may enable more accurate prediction of non-response. METHODS: In all, 130 subjects failing to respond to first-line therapy (cases) between 1990 and 1995 were compared with 673 subjects who responded to therapy (controls) on various demographic and clinical characteristics using logistic regression to create a prognostic index. Variables analysed included the patient history of past TB treatment, weight, age, sex and radiological and bacteriological findings. All subjects also tested negative for HIV status. RESULTS: The chief markers of successful response were x-ray signs and degree of sputum smear positivity. These markers provided a prognostic index with an optimal cutoff providing about 70% sensitivity and 80% specificity. Incorporating further measures obtained through the first 3 months of treatment improved the sensitivity to 80%. CONCLUSION: While this study enabled prediction of the majority of subjects failing to respond to first-line therapy, other factors need to be assessed before recommendations for altering treatment regimens can be made. The prognostic index could be useful in assessing subjects for closer supervision.

Adult↗