A demonstration of cone function plasticity after gene therapy in achromatopsia

Recent advances in regenerative therapy have placed the treatment of previously incurable eye diseases within arms' reach. Achromatopsia is a severe monogenic heritable retinal disease that disrupts cone function from birth, leaving patients with complete colour blindness, low acuity, photosensitivity and nystagmus. While successful gene-replacement therapy in non-primate models of achromatopsia has raised widespread hopes for clinical treatment, it was yet to be determined if and how these therapies can induce new cone function in the human brain. Using a novel multimodal approach, we demonstrate for the first time that gene therapy can successfully activate dormant cone-mediated pathways in children with achromatopsia (CNGA3- and CNGB3-associated, 10-15 years). To test this, we combined functional MRI population receptive field mapping and psychophysics with stimuli that selectively measure cone photoreceptor signalling. We measured cortical and visual cone function before and after gene therapy in four paediatric patients, evaluating treatment-related change against benchmark data from untreated patients (n = 9) and normal-sighted participants (n = 28). After treatment, two of the four children displayed strong evidence for novel cone-mediated signals in visual cortex, with a retinotopic pattern that was not present in untreated achromatopsia and which is highly unlikely to emerge by chance. Importantly, this change was paired with a significant improvement in psychophysical measures of cone-mediated visual function. These improvements were specific to the treated eye, and provide strong evidence for successful read-out and use of new cone-mediated information. These data show for the first time that gene replacement therapy in achromatopsia within the plastic period of development can awaken dormant cone-signalling pathways after years of deprivation. This reveals unprecedented neural plasticity in the developing human nervous system and offers great promise for emerging regenerative therapies.

Binocular Therapy for Childhood Amblyopia Improves Vision Without Breaking Interocular Suppression

Purpose

Amblyopia is a common developmental visual impairment characterized by a substantial difference in acuity between the two eyes. Current monocular treatments, which promote use of the affected eye by occluding or blurring the fellow eye, improve acuity, but are hindered by poor compliance. Recently developed binocular treatments can produce rapid gains in visual function, thought to be as a result of reduced interocular suppression. We set out to develop an effective home-based binocular treatment system for amblyopia that would engage high levels of compliance but that would also allow us to assess the role of suppression in children's response to binocular treatment.

Methods

Balanced binocular viewing therapy (BBV) involves daily viewing of dichoptic movies (with "visibility" matched across the two eyes) and gameplay (to monitor compliance and suppression). Twenty-two children (3-11 years) with anisometropic (n = 7; group 1) and strabismic or combined mechanism amblyopia (group 2; n = 6 and 9, respectively) completed the study. Groups 1 and 2 were treated for a maximum of 8 or 24 weeks, respectively.

Results

The treatment elicited high levels of compliance (on average, 89.4% ± 24.2% of daily dose in 68.23% ± 12.2% of days on treatment) and led to a mean improvement in acuity of 0.27 logMAR (SD 0.22) for the amblyopic eye. Importantly, acuity gains were not correlated with a reduction in suppression.

Conclusions

BBV is a binocular treatment for amblyopia that can be self-administered at home (with remote monitoring), producing rapid and substantial benefits that cannot be solely mediated by a reduction in interocular suppression.

Novel method for detection of reactive oxygen species in vivo in human skeletal muscle

Excessive production of reactive oxygen species (ROS) are implicated in the pathogenesis of numerous disease states. However, direct measurement of in vivo ROS in humans has remained elusive due to limited access to appropriate tissue beds and the inherently short half-lives and high reactivity of ROS. Herein, we describe a novel technique by which to measure in vivo ROS in human skeletal muscle. Microdialysis probes were inserted into the vastus lateralis of eight healthy volunteers. Amplex Ultrared, a highly specific fluorogenic substrate for hydrogen peroxide (H(2)O(2)), and horseradish peroxidase (HRP), were perfused through microdialysis probes, and outflowing dialysate was collected and fluorescence was measured. Extracellular H(2)O(2) that crossed the microdialysis membrane was measured via fluorescence of the dialysate. Superoxide dismutase (SOD) was then added to the inflowing perfusion media to convert any superoxide crossing the microdialysis membrane to H(2)O(2) within the microdialysis probe. Fluorescence significantly increased (P=0.005) upon SOD addition. These data demonstrate the feasibility of measuring both in vivo H(2)O(2) and superoxide in the extracellular environment of human skeletal muscle, providing a technique with a potential application to a wide range of circulatory and metabolic studies of oxidative stress.

Reduced crowding and poor contour detection in schizophrenia are consistent with weak surround inhibition

BACKGROUND

Detection of visual contours (strings of small oriented elements) is markedly poor in schizophrenia. This has previously been attributed to an inability to group local information across space into a global percept. Here, we show that this failure actually originates from a combination of poor encoding of local orientation and abnormal processing of visual context.

METHODS

We measured the ability of observers with schizophrenia to localise contours embedded in backgrounds of differently oriented elements (either randomly oriented, near-parallel or near-perpendicular to the contour). In addition, we measured patients' ability to process local orientation information (i.e., report the orientation of an individual element) for both isolated and crowded elements (i.e., presented with nearby distractors).

RESULTS

While patients are poor at detecting contours amongst randomly oriented elements, they are proportionally less disrupted (compared to unaffected controls) when contour and surrounding elements have similar orientations (near-parallel condition). In addition, patients are poor at reporting the orientation of an individual element but, again, are less prone to interference from nearby distractors, a phenomenon known as visual crowding.

CONCLUSIONS

We suggest that patients' poor performance at contour perception arises not as a consequence of an "integration deficit" but from a combination of reduced sensitivity to local orientation and abnormalities in contextual processing. We propose that this is a consequence of abnormal gain control, a phenomenon that has been implicated in orientation-selectivity as well as surround suppression.

Visual surround suppression in schizophrenia

Compared to unaffected observers patients with schizophrenia (SZ) show characteristic differences in visual perception, including a reduced susceptibility to the influence of context on judgments of contrast – a manifestation of weaker surround suppression (SS). To examine the generality of this phenomenon we measured the ability of 24 individuals with SZ to judge the luminance, contrast, orientation, and size of targets embedded in contextual surrounds that would typically influence the target’s appearance. Individuals with SZ demonstrated weaker SS compared to matched controls for stimuli defined by contrast or size, but not for those defined by luminance or orientation. As perceived luminance is thought to be regulated at the earliest stages of visual processing our findings are consistent with a suppression deficit that is predominantly cortical in origin. In addition, we propose that preserved orientation SS in SZ may reflect the sparing of broadly tuned mechanisms of suppression. We attempt to reconcile these data with findings from previous studies.

The neural correlates of crowding-induced changes in appearance

Object recognition in the peripheral visual field is limited by crowding: the disruptive influence of nearby clutter. Despite its severity, little is known about the cortical locus of crowding. Here, we examined the neural correlates of crowding by combining event-related fMRI adaptation with a change-detection paradigm. Crowding can change the appearance of objects, such that items become perceptually matched to surrounding objects; we used this change in appearance as a signature of crowding and measured brain activity that correlated with the crowded percept. Observers adapted to a peripheral patch of noise surrounded by four Gabor flankers. When crowded, the noise appears oriented and perceptually indistinguishable from the flankers. Consequently, substitution of the noise for a Gabor identical to the flankers ("change-same") is rarely detected, whereas substitution for an orthogonal Gabor ("change-different") is rarely missed. We predicted that brain areas representing the crowded percept would show repetition suppression in change-same trials but release from adaptation in change-different trials. This predicted pattern was observed throughout cortical visual areas V1-V4, increasing in strength from early to late visual areas. These results depict crowding as a multistage process, involving even the earliest cortical visual areas, with perceptual consequences that are increasingly influenced by later visual areas.

White matter microstructure and cognitive function

In recent years, diffusion-weighted magnetic resonance imaging (DW-MRI) has been increasingly used to explore the relationship between white matter structure and cognitive function. This technique uses the passive diffusion of water molecules to infer properties of the surrounding tissue. DW-MRI has been extensively employed to investigate how individual differences in behavior are related to variability in white matter microstructure on a range of different cognitive tasks and also to examine the effect experiential learning might have on brain structural connectivity. Using diffusion tensor tractography, large white matter pathways have been traced in vivo and used to explore patterns of white matter projections between different brain regions. Recent findings suggest that diffusion-weighted imaging might even be used to measure functional differences in water diffusion during task performance. This review describes some research highlights in diffusion-weighted imaging and how this technique can be employed to further our understanding of cognitive function.

Neural correlates of spatial orienting in the human superior colliculus

A natural visual scene contains more information than the visual system has the capacity to simultaneously process, requiring specific items to be selected for detailed analysis at the expense of others. Such selection and inhibition are fundamental in guiding search behavior, but the neural basis of these mechanisms remains unclear. Abruptly appearing visual items can automatically capture attention, but once attention has been directed away from the salient event, return to that same location is slowed. In non-human primates, signals associated with attentional capture (AC) and subsequent inhibition of return (IOR) have been recorded from the superior colliculus (SC)--a structure known to play a pivotal role in reflexive spatial orienting. Here, we sought to establish whether similar signals could be recorded from the human SC, as well as early retinotopic cortical visual areas, where signals associated with AC and IOR have yet to be investigated with respect to oculomotor responses. Using an optimized oculomotor paradigm together with high-field, high-spatial resolution functional magnetic resonance imaging and high-speed eye tracking, we demonstrate that BOLD signal changes recorded from the human SC correlate strongly with our saccadic measures of AC and IOR. A qualitatively similar pattern of responses was found for V1, but only the inhibitory response associated with IOR persisted through V2 and V3. Although the SC plays a role in mediating these automatic attentional biasing signals, the source of these signals is likely to lie in higher cortical areas.

Cortical network for gaze control in humans revealed using multimodal MRI

Functional magnetic resonance imaging (fMRI) techniques allow definition of cortical nodes that are presumed to be components of large-scale distributed brain networks involved in cognitive processes. However, very few investigations examine whether such functionally defined areas are in fact structurally connected. Here, we used combined fMRI and diffusion MRI-based tractography to define the cortical network involved in saccadic eye movement control in humans. The results of this multimodal imaging approach demonstrate white matter pathways connecting the frontal eye fields and supplementary eye fields, consistent with the known connectivity of these regions in macaque monkeys. Importantly, however, these connections appeared to be more prominent in the right hemisphere of humans. In addition, there was evidence of a dorsal frontoparietal pathway connecting the frontal eye field and the inferior parietal lobe, also right hemisphere dominant, consistent with specialization of the right hemisphere for directed attention in humans. These findings demonstrate the utility and potential of using multimodal imaging techniques to define large-scale distributed brain networks, including those that demonstrate known hemispheric asymmetries in humans.

Overlapping functional anatomy for working memory and visual search

Recent behavioural findings using dual-task paradigms demonstrate the importance of both spatial and non-spatial working memory processes in inefficient visual search (Anderson et al. in Exp Psychol 55:301–312, 2008). Here, using functional magnetic resonance imaging (fMRI), we sought to determine whether brain areas recruited during visual search are also involved in working memory. Using visually matched spatial and non-spatial working memory tasks, we confirmed previous behavioural findings that show significant dual-task interference effects occur when inefficient visual search is performed concurrently with either working memory task. Furthermore, we find considerable overlap in the cortical network activated by inefficient search and both working memory tasks. Our findings suggest that the interference effects observed behaviourally may have arisen from competition for cortical processes subserved by these overlapping regions. Drawing on previous findings (Anderson et al. in Exp Brain Res 180:289–302, 2007), we propose that the most likely anatomical locus for these interference effects is the inferior and middle frontal cortex of the right hemisphere. These areas are associated with attentional selection from memory as well as manipulation of information in memory, and we propose that the visual search and working memory tasks used here compete for common processing resources underlying these mechanisms.

Monocular signals in human lateral geniculate nucleus reflect the Craik-Cornsweet-O'Brien effect

The human visual system has a remarkable ability to accurately estimate the relative brightness of adjacent objects despite large variations in illumination. However, the lightness of two identical equiluminant gray regions can appear quite different when a light-dark luminance transition falls between them. This illusory brightness "filling-in" phenomenon, the Craik-Cornsweet-O'Brien (CCOB) illusion, exposes fundamental assumptions made by the visual system in estimating lightness, but its neural basis remains unclear. While the responses of high-level visual cortex can be correlated with perception of the CCOB, simple computational models suggest that the effect may originate from a much lower level, possibly subcortical. Here, we used high spatial resolution functional magnetic resonance imaging to show that the CCOB illusion is strongly correlated with signals recorded from the human lateral geniculate nucleus. Moreover, presenting the light and dark luminance transitions that induce the CCOB effect separately to each eye abolishes the illusion, suggesting that it depends on eye-specific signals. Our observations suggest that the CCOB effect arises from signals in populations of monocular neurons very early in the human geniculostriate visual pathway.

Common cortical loci are activated during visuospatial interpolation and orientation discrimination judgements

There is a wealth of literature on the role of short-range interactions between low-level orientation-tuned filters in the perception of discontinuous contours. However, little is known about how spatial information is integrated across more distant regions of the visual field in the absence of explicit local orientation cues, a process referred to here as visuospatial interpolation (VSI). To examine the neural correlates of VSI high field functional magnetic resonance imaging was used to study brain activity while observers either judged the alignment of three Gabor patches by a process of interpolation or discriminated the local orientation of the individual patches. Relative to a fixation baseline the two tasks activated a largely over-lapping network of regions within the occipito-temporal, occipito-parietal and frontal cortices. Activated clusters specific to the orientation task (orientation>interpolation) included the caudal intraparietal sulcus, an area whose role in orientation encoding per se has been hotly disputed. Surprisingly, there were few task-specific activations associated with visuospatial interpolation (VSI>orientation) suggesting that largely common cortical loci were activated by the two experimental tasks. These data are consistent with previous studies that suggest higher level grouping processes -putatively involved in VSI- are automatically engaged when the spatial properties of a stimulus (e.g. size, orientation or relative position) are used to make a judgement.

A Role for Spatial and Nonspatial Working Memory Processes in Visual Search

Searching a cluttered visual scene for a specific item of interest can take several seconds to perform if the target item is difficult to discriminate from surrounding items. Whether working memory processes are utilized to guide the path of attentional selection during such searches remains under debate. Previous studies have found evidence to support a role for spatial working memory in inefficient search, but the role of nonspatial working memory remains unclear. Here, we directly compared the role of spatial and nonspatial working memory for both an efficient and inefficient search task. In Experiment 1, we used a dual-task paradigm to investigate the effect of performing visual search within the retention interval of a spatial working memory task. Importantly, by incorporating two working memory loads (low and high) we were able to make comparisons between dual-task conditions, rather than between dual-task and single-task conditions. This design allows any interference effects observed to be attributed to changes in memory load, rather than to nonspecific effects related to “dual-task” performance. We found that the efficiency of the inefficient search task declined as spatial memory load increased, but that the efficient search task remained efficient. These results suggest that spatial memory plays an important role in inefficient but not efficient search. In Experiment 2, participants performed the same visual search tasks within the retention interval of visually matched spatial and verbal working memory tasks. Critically, we found comparable dual-task interference between inefficient search and both the spatial and nonspatial working memory tasks, indicating that inefficient search recruits working memory processes common to both domains.

Human intraparietal sulcus (IPS) and competition between exogenous and endogenous saccade plans

How are stimulus-driven reflexes generated, and what controls their competition with voluntary action? The saccadic reflex to look towards an abrupt visual onset (prosaccade) has been associated with the retinotectal and magnocellular pathways, which rapidly convey signals to the superior colliculus and cortical eye fields. Such stimulus-driven reflexes need to be suppressed when making an eye movement in the opposite direction (antisaccade), resulting in a cost in saccade latency. We compared the latencies of pro- and anti-saccades elicited by conventional luminance stimuli with those evoked by stimuli visible only to short-wave-sensitive cones (S cones) embedded in dynamic luminance noise. Critically, the retinotectal and magnocellular pathways are functionally blind to such stimuli. Compared to luminance stimuli, antisaccade latency costs were significantly reduced for 'S-cone' stimuli. This behavioural interaction is consistent with reduced competition between reflexive and endogenous saccade plans when S-cone stimuli are employed, while other processes involved in making an antisaccade, such as changing preparatory set or generating an endogenous saccade, are predicted to be equivalent for each kind of stimulus. Using fMRI, we found that activity in the right intraparietal sulcus (IPS) mirrored the behavioural interaction in saccade latencies. Thus, the right IPS appears to index the degree of competition between exogenous and endogenous saccade plans, showing the activity pattern predicted for an area involved in suppressing the saccade reflex. Furthermore, signals recorded from the superior colliculus showed the reverse pattern of responses, consistent with a direct inhibitory influence of IPS on SC.

Combined orientation and colour information in human V1 for both L-M and S-cone chromatic axes

Although it is widely held that colour and form are processed separately in early visual cortex, there is growing evidence that primary visual cortex (V1) may show some joint selectivity for orientation and colour. Colour is supplied to V1 via two very different pathways: the parvocellular pathway (which also supports detailed form processing) carries L-M ("red-green") chromatic information, while a koniocellular pathway carries S-cone ("lilac-yellow") information. Therefore on entering V1, S-cone information is segregated from the pathways carrying form information, while L-M information is not. Whether signals from neuronal populations in human V1 reflect combined orientation and S-cone information has not been systematically addressed. We used fMRI in combination with a multivariate data analysis technique to investigate whether BOLD signals recorded from V1 contain information that could directly discriminate between orientations based on different types of chromatic information. We found selectivity in V1 for L-M and luminance-defined orientation signals, and most interestingly, also for S-cone defined orientation. We also found similarly successful orientation discrimination for both colour dimensions in V2 and V3. These results imply that a proportion of cells throughout human visual cortex show joint sensitivity to both colour and orientation. We discuss also the potential role of feedback to V1 from higher visual areas.

Involvement of prefrontal cortex in visual search

Visual search for target items embedded within a set of distracting items has consistently been shown to engage regions of occipital and parietal cortex, but the contribution of different regions of prefrontal cortex remains unclear. Here, we used fMRI to compare brain activity in 12 healthy participants performing efficient and inefficient search tasks in which target discriminability and the number of distractor items were manipulated. Matched baseline conditions were incorporated to control for visual and motor components of the tasks, allowing cortical activity associated with each type of search to be isolated. Region of interest analysis was applied to critical regions of prefrontal cortex to determine whether their involvement was common to both efficient and inefficient search, or unique to inefficient search alone. We found regions of the inferior and middle frontal cortex were only active during inefficient search, whereas an area in the superior frontal cortex (in the region of FEF) was active for both efficient and inefficient search. Thus, regions of ventral as well as dorsal prefrontal cortex are recruited during inefficient search, and we propose that this activity is related to processes that guide, control and monitor the allocation of selective attention.

Temporal dynamics of parietal cortex involvement in visual search

The functional-neuroanatomic relationship that describes the involvement of the parietal cortex in visual search was investigated using repetitive transcranial magnetic stimulation (rTMS; 10 Hz, 500 ms in duration). Twelve adult participants performed feature-based visual search for a unique letter-without eye movements-under conditions that involved manipulations of search efficiency (efficient versus inefficient) and target-selection demands (set-size: 4 versus 10). rTMS was applied over the right posterior parietal cortex at the onset of the search array for all factorial conditions (0-500 ms); stimulation was additionally administered at 500 ms post-array onset (500-1000 ms) during inefficient search (set-size 10). Stimulation over the primary sensorimotor cortex served as a within-subjects control condition, and eye movements were monitored continuously. Significant increases in reaction time were restricted to parietal stimulation during inefficient search (set-size 10), with interference observed when rTMS was administered at the onset of the search array and at 500 ms post-array onset. The early effect was confined to target-present trials and the late effect was confined to target-absent trials, which may indicate temporally dissociable parietal involvement in target detection and response-based selection and/or search termination, respectively. Error rates did not vary significantly as a function of any of the independent variables. Taken together, these results are consistent with evidence from functional magnetic resonance studies indicating that inefficient feature-based visual search requires an intact parietal cortex, and also indicate that the parietal cortex is involved in inefficient search later than has been previously reported.

Modifiable dietary habits and their relation to metabolic abnormalities in men and women with human immunodeficiency virus infection and fat redistribution

We assessed the relationship between dietary intake, body composition, and metabolic parameters in 85 consecutive human immunodeficiency virus (HIV)-infected patients with fat redistribution. Dietary history and values for fasting glucose, insulin, lipids, and oral glucose tolerance were obtained for 62 men and 23 women with HIV infection and fat redistribution (mean age +/- standard error of the mean [SEM], 43.5+/-0.9 years; mean body mass index [BMI] +/- SEM, 26.3+/-0.5 kg/m2). A multivariate regression analysis was used to predict insulin area under the curve (AUC) following the oral glucose tolerance test; this included age, sex, BMI, waist-to-hip ratio, kilocalories, duration of protease inhibitor (PI) use, fat redistribution pattern, alcohol intake, dietary fiber intake, and polyunsaturated-to-saturated (P:S) fat ratio. Only age (P=.004), PI use duration (P=.02), and P:S fat ratio (P=.003) were positively associated with insulin AUC. Dietary fiber intake was inversely associated with the insulin AUC (P=.001). In a similar analysis, alcohol consumption was a significant positive predictor of low-density lipoprotein cholesterol. Polyunsaturated fats, fiber, and alcohol are strongly associated with insulin resistance and hyperlipidemia in this population and may be important targets for dietary modification.

Body composition and energy balance: lack of effect of short-term hormone replacement in postmenopausal women

Postmenopausal women (PMW) commonly believe that hormone replacement (HR) leads to weight gain, and fear of weight gain and/or an actual increase in weight is one of the principle reasons evoked for the discontinuation of HR. However, the potential effects of physiologic HR on body composition have yet to be separated from the effects of lifestyle or aging. Therefore, we examined the effect of short-term hormone replacement and age on alterations in weight, body composition, and energy balance. A prospective study of 28 healthy PMW aged 45 to 55 years (younger PMW, studies completed n = 18) and 70 to 80 years (older PMW, studies completed n = 15) was conducted. The last menstrual period was more than 12 months previously. The women had a body mass index (BMI) less than 30 kg/m(2) and were taking no medication. Subjects were studied at baseline, after 1 month of transdermal estrogen (Estraderm, 50 microg/day) administration (E2), followed by a further month of transdermal estrogen with progesterone (100 mg per vagina twice daily) for the final 7 days (E2 + P). Anthropometric measurements and energy assessments were performed at each visit. Physiologic HR was achieved in each subject, and there was no difference between levels achieved in older and younger women. Resting energy expenditure and activity level were positively correlated with fat-free mass (P <.0001), while energy intake was not. Resting energy expenditure was lower in older compared with younger PMW when adjusted for fat-free mass (P <.005). Energy intake was also lower in the older PMW when corrected for fat-free mass (P <.0001); as was activity level (P <.05). There was no effect of hormonal treatment on any of the parameters measured. Changes in weight from baseline for E2 (0.37 +/- 0.25 and 0.61 +/- 0.27 kg in younger and older) and E2 + P (0.11 +/- 0.38 and 0.28 +/- 0.31 kg) were not statistically significant. In addition, there was no difference in BMI, fat mass, fat-free mass, total body water, or waist-to-hip ratio (WHR) between groups or with hormonal treatment. In conclusion, short-term transdermal HR is not associated with significant changes in weight or other anthropometric measures in younger or older PMW. These studies confirm the decrease in energy expenditure that occurs with aging, but indicates that there is no effect of HR on resting energy expenditure.

The boundary layer of swimming fish

Tangential and normal velocity profiles of the boundary layer surrounding live swimming fish were determined by digital particle tracking velocimetry, DPTV. Two species were examined: the scup Stenotomus chrysops, a carangiform swimmer, and the smooth dogfish Mustelus canis, an anguilliform swimmer. Measurements were taken at several locations over the surfaces of the fish and throughout complete undulatory cycles of their propulsive motions. The Reynolds number based on length, Re, ranged from 3×10(3) to 3×10(5). In general, boundary layer profiles were found to match known laminar and turbulent profiles including those of Blasius, Falkner and Skan and the law of the wall. In still water, boundary layer profile shape always suggested laminar flow. In flowing water, boundary layer profile shape suggested laminar flow at lower Reynolds numbers and turbulent flow at the highest Reynolds numbers. In some cases, oscillation between laminar and turbulent profile shapes with body phase was observed. Local friction coefficients, boundary layer thickness and fluid velocities at the edge of the boundary layer were suggestive of local oscillatory and mean streamwise acceleration of the boundary layer. The behavior of these variables differed significantly in the boundary layer over a rigid fish. Total skin friction was determined. Swimming fish were found to experience greater friction drag than the same fish stretched straight in the flow. Nevertheless, the power necessary to overcome friction drag was determined to be within previous experimentally measured power outputs. No separation of the boundary layer was observed around swimming fish, suggesting negligible form drag. Inflected boundary layers, suggestive of incipient separation, were observed sporadically, but appeared to be stabilized at later phases of the undulatory cycle. These phenomena may be evidence of hydrodynamic sensing and response towards the optimization of swimming performance.

Assessment of macronutrient and micronutrient intake in women with anorexia nervosa

OBJECTIVE

The purpose of this study is to evaluate the accuracy of diet history compared to observed food intake in the nutritional assessment of women with anorexia nervosa (AN) and healthy age-matched controls.

METHOD

One-month diet history was compared to 1-day observed food intake in 30 women with AN and 28 control subjects.

RESULTS

Reported intake by diet history was similar to observed intake for macronutrient composition and fat intake for patients with AN. Reported energy intake was higher than observed intake (1,602 +/- 200 kcal vs. 1,289 +/- 150 kcal, p <.05), but was in agreement with predicted energy expenditure by the Harris-Benedict equation (1,594 +/- 18 kcal, p =.97) in patients with AN. Micronutrient intake by diet history was highly correlated with observed intake in patients with AN. More than one half of the patients with AN failed to meet the recommended dietary allowance (RDA) for vitamin D, calcium, folate, vitamin B12, zinc, magnesium, and copper when assessed by diet history. In contrast to patients with AN, diet history did not correlate with observed intake of energy, macronutrients, or most micronutrients among the controls.

DISCUSSION

Diet history is an accurate tool to assess fat intake and macronutrient composition in patients with AN and demonstrates significant micronutrient deficiencies in this population. The agreement between total energy intake and predicted energy expenditure supports the overall utility of the diet history in the nutritional assessment of patients with AN.

Comparison of total body potassium with other techniques for measuring lean body mass in men and women with AIDS wasting

BACKGROUND

Lean body mass is an important predictor of survival and functional status in patients with AIDS wasting. The bias between different techniques for assessing body composition in AIDS wasting is not known.

DESIGN

We compared total body potassium (TBK) with fat-free mass (FFM) determined by dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA), and skinfold-thickness measurement (SKF) in 132 patients (63 men, 69 women) with AIDS wasting (weight < 90% of ideal body weight, or weight loss > 10% of original, or both). None of the subjects exhibited clinical lipodystrophy. Comparisons were made by using different BIA equations.

RESULTS

Lean body mass determined by DXA was highly correlated with TBK in men (r = 0.79, P: < 0.0001) and women (r = 0.84, P: < 0.0001). FFM(BIA) and FFM(DXA) were significantly different (P: < 0.01 in men and P: < 0.0001 in women). The difference between FFM(DXA) and FFM(BIA) was significantly greater with greater weight and body fat, particularly in HIV-infected women (r = -0.39, P: = 0.001 for weight; r = -0.60, P: < 0.0001 for fat). The comparability of FFM and fat mass determined by DXA and BIA was dependent on the specific BIA equation used. Among men, no single BIA equation was more highly predictive of fat mass and FFM in comparison with DXA.

CONCLUSIONS

The differences between DXA, BIA, and SKF in the determination of fat mass and FFM are significant in patients with AIDS wasting. BIA overestimates FFM compared with DXA in those with greater body fat. Standard BIA equations may not accurately estimate FFM and fat mass in men and women with AIDS wasting.

The mechanics of locomotion in the squid Loligo pealei: locomotory function and unsteady hydrodynamics of the jet and intramantle pressure

High-speed, high-resolution digital video recordings of swimming squid (Loligo pealei) were acquired. These recordings were used to determine very accurate swimming kinematics, body deformations and mantle cavity volume. The time-varying squid profile was digitized automatically from the acquired swimming sequences. Mantle cavity volume flow rates were determined under the assumption of axisymmetry and the condition of incompressibility. The data were then used to calculate jet velocity, jet thrust and intramantle pressure, including unsteady effects. Because of the accurate measurements of volume flow rate, the standard use of estimated discharge coefficients was avoided. Equations for jet and whole-cycle propulsive efficiency were developed, including a general equation incorporating unsteady effects. Squid were observed to eject up to 94 % of their intramantle working fluid at relatively high swimming speeds. As a result, the standard use of the so-called large-reservoir approximation in the determination of intramantle pressure by the Bernoulli equation leads to significant errors in calculating intramantle pressure from jet velocity and vice versa. The failure of this approximation in squid locomotion also implies that pressure variation throughout the mantle cannot be ignored. In addition, the unsteady terms of the Bernoulli equation and the momentum equation proved to be significant to the determination of intramantle pressure and jet thrust. Equations of propulsive efficiency derived for squid did not resemble Froude efficiency. Instead, they resembled the equation of rocket motor propulsive efficiency. The Froude equation was found to underestimate the propulsive efficiency of the jet period of the squid locomotory cycle and to overestimate whole-cycle propulsive efficiency when compared with efficiencies calculated from equations derived with the squid locomotory apparatus in mind. The equations for squid propulsive efficiency reveal that the refill period of squid plays a greater role, and the jet period a lesser role, in the low whole-cycle efficiencies predicted in squid and similar jet-propelled organisms. These findings offer new perspectives on locomotory hydrodynamics, intramantle pressure measurements and functional morphology with regard to squid and other jet-propelled organisms.

A revised model for the structure and function of the lactose permease. Evidence that a face on transmembrane segment 2 is important for conformational changes

The lactose permease is an integral membrane protein that cotransports H(+) and lactose into the bacterial cytoplasm. Previous work has shown that bulky substitutions at glycine 64, which is found on the cytoplasmic edge of transmembrane segment 2 (TMS-2), cause a substantial decrease in the maximal velocity of lactose uptake without significantly affecting the K(m) values (Jessen-Marshall, A. E., Parker, N. J., and Brooker, R. J. (1997) J. Bacteriol. 179, 2616-2622). In the current study, mutagenesis was conducted along the face of TMS-2 that contains glycine-64. Single amino acid substitutions that substantially changed side-chain volume at codons 52, 57, 59, 63, and 66 had little or no effect on transport activity, whereas substitutions at codons 49, 53, 56, and 60 were markedly defective and/or had lower levels of expression. According to helical wheel plots, Phe-49, Ser-53, Ser-56, Gln-60, and Gly-64 form a continuous stripe along one face of TMS-2. Several of the TMS-2 mutants (S56Y, S56L, S56Q, Q60A, and Q60V) were used as parental strains to isolate mutants that restore transport activity. These mutations were either first-site mutations or second-site suppressors in TMS-1, TMS-2, TMS-7 or TMS-11. A kinetic analysis showed that the suppressors had a higher rate of lactose transport compared with the corresponding parental strains. Overall, the results of this study are consistent with the notion that a face on TMS-2, containing Phe-49, Ser-53, Ser-56, Gln-60, and Gly-64, plays a critical role in conformational changes associated with lactose transport. We hypothesize that TMS-2 slides across TMS-7 and TMS-11 when the lactose permease interconverts between the C1 and C2 conformations. This idea is discussed within the context of a revised model for the structure of the lactose permease.

Effects of short-term hormone replacement on serum leptin levels in postmenopausal women

OBJECTIVE

Leptin is a hormone which is secreted by adipocytes and appears to influence the reproductive axis. Previous studies have demonstrated higher leptin levels in relation to body fat mass in women compared to men, higher levels in normally cycling compared to postmenopausal women, and a decrease in leptin levels with increased age. The purpose of this study was to determine whether oestrogen replacement with or without progesterone increases serum leptin levels in postmenopausal women, independently of changes in body fat, and to determine if ageing affects leptin levels at baseline or in response to hormone replacement.

PATIENTS

Twenty-one healthy postmenopausal women on no hormone replacement were studied at baseline, after 1 month of oestrogen (E2: estraderm 50 microg/day) and after a further month of oestrogen and 7 days of progesterone (P: progesterone 100 mg per vagina bid) designed to achieve physiological hormone levels. Subjects included 11 younger (45-55 years) and 10 older (70-80 years) postmenopausal women.

RESULTS

The relationship between leptin and the absolute fat mass (% body fat x weight [kg]) at baseline was not different between the younger and older postmenopausal women. The adequacy of physiological hormone replacement was confirmed in all subjects. Despite the absence of an effect of hormone replacement on weight, body mass index (BMI), % and absolute fat mass (bioimpedance) or waist-hip ratio, there was an increase in serum leptin levels with hormone replacement (15.4 +/- 1.7, 17.6 +/- 1.7, and 18.1 +/- 1.6 microg/l; mean +/- SEM at baseline, with E2, and with E2 + P, respectively; P < 0.001 vs. baseline) for the group as a whole. An increase in leptin with hormonal treatment was seen in both the younger (15.1 +/- 2.1, 18.1 +/- 2.4, and 18.5 +/- 1.9 microg/l; P < 0.01) and the older (15.7 +/- 2.8, 17.0 +/- 2.5, 17.7 +/- 2.8 microg/l; P = 0.06) postmenopausal women.

CONCLUSIONS

(1) Short-term physiological oestrogen replacement increases serum leptin levels in postmenopausal women independently of changes in fat mass; and (2) physiological progesterone replacement does not influence leptin levels in postmenopausal women.

Structure and mechanics of the squid mantle

The goal of this study was to obtain a complete description of the elastic modulus and hysteresis of the mantle tissue of the squid Loligo pealei over the entire functional region of the mantle. In addition, in vivo strains were measured to allow calculations of the amount of energy stored and returned in each region of the mantle studied, and microscopic analysis of the tissue was carried out with the aim of correlating macroscopic properties with microscopic structure. The results of dynamic tissue tests indicate that mean elastic moduli for each of the 35 mantle positions tested ranged from 5.0×10(5) to 1.2×10(6)N m-2. The elastic modulus varied within a narrow range, in no predictable manner. Mean hysteresis values for each position varied from 19.7 % to 27.3 % with no discernible patterns found either around or along the mantle. In vivo mantle strains peaked in the middle (lengthwise) of the mantle and declined towards both ends, and the absolute strains increased with increasing swimming velocity. Energy storage calculations showed that most energy was stored in the middle of the mantle, with an increase in storage with increased swimming velocity. Microscopic tissue analysis found direct correlations between macroscopic properties and microscopic characteristics, and electron microscopical analysis of all three types of intramuscular fibre revealed that all three types are collagenous in nature.

Impact of binge eating on metabolic and leptin dynamics in normal young women

Well defined eating disorders such as anorexia nervosa and bulimia are associated with significant known health risks. Although binge eating behavior is increased in unsuccessfully dieting obese women, other health implications of this common eating pattern are unknown. We hypothesized that ingestion of an entire day's calories at one time in the evening, a common eating practice among Americans, would lead to disruptions in glucose, insulin, and leptin metabolism and in menstrual cyclicity, even in healthy young women. Seven lean women without a history of eating disorders were studied on two occasions separated by one or two menstrual cycles. During one admission, they ate three regular meals plus a snack on each of 3 days. On the other admission, they ate the same number of calories, macronutrient matched to the normal diet, in a single evening meal. Glucose, insulin, and leptin were measured frequently for 12-14 h beginning at 0800 h on the third day of each diet, and an insulin tolerance test was performed while the subjects were fasting on the fourth day. Daily blood samples were obtained until ovulation was documented to assess any impact on menstrual function. Ingestion of an entire day's calories at dinner resulted in a significant increase in fasting glucose levels and a dramatic increase in insulin responses to the evening meal. The diurnal pattern of leptin secretion was altered, such that the gradual rise in leptin from 0800 h observed during the normal diet was abolished, and leptin did not begin to rise during the binge diet until at least 2 h after the evening meal. No changes were demonstrated in insulin sensitivity, follicular growth, or ovulation between the two diets. We conclude that 1) ingestion of a large number of calories at one time (binge eating) impacts metabolic parameters even when total calories and macronutrients are appropriate for weight; 2) the timing of energy intake is an independent determinant of the diurnal rhythm of leptin secretion, indicating a relatively acute affect of energy balance on leptin dynamics; 3) the mechanism of exaggerated insulin secretion after a binge meal remains to be determined, but may be related to the altered diurnal pattern of leptin secretion; and 4) as most binge eating episodes in the population are associated with the ingestion of excess calories, it is hypothesized that binge eating behavior is associated with even greater metabolic dysfunction than that described herein.

Nucleotide sequence of a resistance breaking mutant of southern bean mosaic virus

SBMV-S is a resistance-breaking mutant of an Arkansas isolate of the bean strain of southern bean mosaic virus (SBMV-BARK) that is able to move systemically in Phaseolus vulgaris cvs. Pinto and Great Northern, whereas the wild-type SBMV-BARK causes local necrotic lesions and is restricted to the inoculated leaves of these hosts. Sequence analysis of the 4136 nucleotide genomes of SBMV-BARK and SBMV-S revealed seven nucleotide differences, but only four deduced amino acid changes. A single amino acid change occurred in the C-terminal region of the putative RNA-dependent RNA polymerase and three differences were identified in the N-terminal portion of the virus coat protein. SBMV-BARK and SBMV-S were compared with other sobemoviruses and were found to contain a high level of nucleotide sequence identity (91.3%) to SBMV-B. Unlike SBMV-B however, SBMV-BARK and SBMV-S contained four putative overlapping open reading frames, making them more similar in genome organization to the cowpea strain, SBMV-C. The possibility exists that mutations or even errors, that resulted in mis-identification of open reading frames, occurred in previously published information on nucleotide sequence and genomic organization for SBMV-B.

Using quantitative CT to assess adipose distribution in adult men with acquired hypogonadism

OBJECTIVE

Quantitative CT is a powerful tool that may be used to assess distribution of adipose and lean mass and bone mineral density in specific anatomic compartments. Testosterone deficiency (hypogonadism) is increasingly recognized in adult men and is associated with osteoporosis, diminished strength, and an increase in cardiovascular risk. We used quantitative CT to determine whether hypogonadism is associated with fat redistribution and altered bone density.

SUBJECTS AND METHODS

Quantitative CT was performed at the level of the L4 vertebra in 26 men with adult onset testosterone deficiency and 17 eugonadal men of similar body mass index and age. Adipose area in the subcutaneous, visceral, and skeletal muscle areas was determined and trabecular bone density was measured. Values between the groups were compared using t tests.

RESULTS

The ages of the hypogonadal and eugonadal men were 52 +/- 14 years and 51 +/- 8 years (p value not significant), respectively. Subcutaneous fat area was higher in the testosterone-deficient men than in the control subjects (270 +/- 101 cm2 versus 202 +/- 111 cm2; p = .046). Muscle fat area was higher in the hypogonadal men (6 +/- 3 cm2 versus 2 +/- 1 cm2; p = .001). Measurements of visceral fat were similar for both groups. Trabecular bone density was lower in the hypogonadal than in the eugonadal men (112 +/- 38 mg K2HPO4/dl versus 148 +/- 34 mg K2HPO4/dl, respectively; p = .003).

CONCLUSION

Our findings indicate that testosterone deficiency is associated with a decrease in bone density and a redistribution of fat. Quantitative CT is a sensitive method that may be useful in determining alterations in regional adipose deposition in hypogonadal men and in evaluating the benefit of interventional therapy such as testosterone replacement.

Seed transmission of cucumber mosaic virus in spinach

ABSTRACT Spinach (Spinacia oleracea) seed from a commercial breeding line suspected of harboring cucumber mosaic virus (CMV) was analyzed for seed transmission of the virus. Initial seed grow-out tests and enzymelinked immunosorbent assay studies indicated that CMV was present in this seed lot at a level of nearly 15%. To verify these results and gain insight into the mechanism of seed transmission, four combinations of crosses between healthy and/or infected parent plants were conducted. None of the spinach seedlings derived from crossing healthy male and healthy female plants contained CMV, whereas a portion of seedlings derived from all of the other three crosses, i.e., healthy male and infected female, infected male and healthy female, and infected male and infected female plants, were infected with CMV. The results demonstrate that CMV is seed transmitted in spinach and indicate that both male and female parent plants can serve as infection sources. Ultrastructural studies, including immunogold labeling, revealed the presence of virus particles in the cytoplasm of ovary wall cells, ovule integuments and nucellus, anther, and seed-coat cells, as well as fine fibril-containing vesicles and electron-dense inclusions of amorphous aggregates in the central vacuoles of these cells. In addition, reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify 860-bp cDNA fragments containing the CMV coat protein (CP) gene from the embryo, endosperm, and pollen tissues of CMV-infected plants. Taken together, these studies indicate that CMV occurs in virtually all spinach reproductive tissues. Analysis of several RT-PCR amplified and cloned CP genes and flanking sequences from parent and progeny plants revealed that the spinachinfecting CMV was a member of subgroup II. Furthermore, cDNA sequencing and restriction endonuclease mapping consistently revealed two sequence variants, designated SP103 and SP104, in most plants analyzed. These data suggest that there may have been mixed infections of two distinct, seed-transmitted CMV variants in spinach.

First Report of Cowpea Aphid-Borne Mosaic Potyvirus from Cowpeas Grown Commercially in the U.S

Cowpea aphid-borne mosaic potyvirus (CABMV) is one of several seed-borne viruses known to limit cowpea (Vigna unguiculata (L.) Walp. subsp. unguiculata) production in Africa, Europe, and Asia, but CABMV has not been reported on commercially grown cowpeas in the United States (1). However, a sesame (Sesamum indicum L.)-infecting isolate of CABMV was recently characterized from plants growing near cowpea introduction plots in Georgia (2). In February 1997, we received samples of three seed lots of cowpea cv. Chinese Red that had been harvested in southern Texas during 1996. Approximately 28% of the plants grown from these seed lots expressed strong mosaic symptoms on primary and trifoliate leaves. Viruslike symptoms were reproduced following mechanical transmission to plants of Chinese Red cowpea, Nicotiana benthamiana, and soybean (Glycine max L.) cv. Lee. When Coronet and Pinkeye Purple Hull-BVR cowpeas were inoculated with sap extracts from symptomatic Chinese Red plants, chlorotic lesions developed on inoculated leaves, but only Coronet plants supported symptomless systemic infections. Similarly inoculated plants of Chenopodium quinoa (L.) and common bean (Phaseolus vulgaris L.) cvs. Pinto and Black Valentine developed localized chlorotic lesions. In Ouchterlony gel diffusion assays, extracts from symptomatic cowpea plants did not react with antisera to blackeye cowpea mosaic potyvirus (BlCMV), cucumber mosaic cucu-movirus (CMV), southern bean mosaic sobemovirus, cowpea mosaic comovirus, cowpea severe mosaic comovirus, or cowpea chlorotic mottle bromovirus. In the indirect enzyme-linked immunosorbent assay, sap extracts from symptomatic plants reacted with antiserum to CABMV, giving OD values at A₄₀₅ of 0.10 to 0.25, and reacted weakly with antiserum to BlCMV, with OD values at A₄₀₅ less than 0.035. Extracts from healthy control plants gave OD values at A₄₀₅ less than 0.010. No positive reactions were obtained with antisera to bean yellow mosaic potyvirus, peanut mottle potyvirus, soybean mosaic potyvirus, or CMV. To our knowledge, this is the first report of CABMV in commercially grown cowpea from the U.S. References: (1) A. G. Gillaspie et al. Plant Dis. 79:388, 1995. (2) H. R. Pappu et al. Arch. Virol. 142:1, 1997.

Identification and partial characterization of Arkansas isolates of chicken anemia virus

Chickens from both broiler and broiler breeder pullet flocks experiencing symptoms of chicken anemia virus (CAV) infection were first observed at the Poultry Health Research Laboratory at the University of Arkansas in September 1992. Flocks had experienced higher than normal mortality with subcutaneous hemorrhages on the wings, neck, and thorax. Postmortem and histopathologic evaluation revealed thymus and bursal atrophy and lesions consistent with those reported for CAV infection. Because this infection had not previously been observed by Poultry Health Research Laboratory personnel in Arkansas-grown chickens, the establishment of a definitive diagnosis was deemed important. The presence of CAV was established by infecting MSB-1 cells with pooled liver homogenates from groups of 10 specific-pathogen-free chickens that had previously been inoculated in an attempt to experimentally reproduce the disease observed in the field. Cytopathic effects in the infected MSB-1 cells were first evident following the fifth passage. Indirect fluorescent antibody technique identified infected MSB-1 cells following at least five blind passages. To further confirm the presence of CAV, a polymerase chain reaction (PCR) technique was used to amplify a specific portion of the virus genome from infected MSB-1 cells and tissue extracts from several submitted chickens. Sequence analysis of a 186-bp PCR amplification product revealed that the Arkansas isolate was very similar to the Cuxhaven-1 isolate (99.5% sequence identity).

Determinants of abnormal gonadotropin secretion in clinically defined women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder of reproductive age women characterized in its broadest definition by the presence of oligoamenorrhea and hyperandrogenism and the absence of other disorders. Defects of gonadotropin secretion, including an elevated LH level, elevated LH to FSH ratio, and an increased frequency and amplitude of LH pulsations have been described, but the prevalence of these defects in a large, unbiased population of PCOS patients has not been determined. Sixty-one women with PCOS defined by oligomenorrhea and hyperandrogenism and 24 normal women in the early follicular phase had LH samples obtained every 10 min for 8-12 h. Pool LH levels from the frequent sampling studies were within the normal range in the 9 PCOS patients (14.8%) who were studied within 21 days after a documented spontaneous ovulation. Excluding these post-ovulatory patients, 75.0% of the PCOS patients had an elevated pool LH level (above the 95th percentile of the normal controls), and 94% had an elevated LH to FSH ratio. In the anovulatory PCOS patients, pool LH correlated positively with 17-OH progesterone (R = 0.30, P = 0.03), but not with estradiol, estrone, testosterone, androstenedione, or DHEA-S. Pool LH and LH to FSH ratio correlated positively with LH pulse frequency (R = 0.40, P = 0.004 for pool LH, and R = 0.39; P = 0.005 for LH/FSH). There was also a strong negative correlation between pool LH and body mass index (BMI) (R = -0.59, P < 10(-5)). The relationship between BMI and LH secretion in the PCOS patients appeared to be strongest with body fatness, as pool LH was correlated inversely with percent body fat, whether measured by skinfolds (R = -0.61, P < 10(-5)), bioimpedance (R = -0.55, P < 10(-4)), or dual energy x-ray absorptiometry (DEXA) (R = -0.70, P = 0.001; n = 18 for DEXA only). By DEXA, the only body region that was highly correlated with pool LH was the trunk (R = -0.71, P = 0.001). The relationship between body fatness and LH secretion occurred via a decrease in LH pulse amplitude (R = -0.63, P < 10(-5) for BMI; R = -0.58, P < 10(-4) for bioimpedance; and R = -0.64, P = 0.004 for whole body DEXA), with no significant change in pulse frequency with increasing obesity (R = -0.17, P = 0.23 for BMI).

IN CONCLUSION

1) the prevalence of gonadotropin abnormalities is very high in women with PCOS selected on purely clinical grounds, but is modified by recent spontaneous ovulation; 2) the positive relationship between LH pulse frequency and both pool LH and LH to FSH ratio supports the hypothesis that a rapid frequency of GnRH secretion may play a key etiologic role in the gonadotropin defect in PCOS patients; 3) pool LH and LH pulse amplitude are inversely related to body mass index and percent body fat in a continuous fashion; and 4) the occurrence of a continuous spectrum of gonadotropin abnormalities varying with body fat suggests that nonobese and obese patients with PCOS do not represent distinct pathophysiologic subsets of this disorder.

Scallop Shells Exhibit Optimization of Riblet Dimensions for Drag Reduction

Drag reduction by streamwise surface grooves, or riblets, has been observed by engineers and has been suggested to apply to certain biological systems. Drag reductions as high as 8% have been observed (1), leading to practical nautical and aeronautical applications (2, 3, 4). The shells of several species of scallop, including Placopecten magellanicus, display riblets arranged radially, and therefore roughly parallel to the flow during swimming (Fig. 1a). The dimensions of these riblets on particular scallops fall within the region necessary for drag reduction at experimentally measured swimming speeds. Moreover, the actual spacing of the riblets gradually migrates into the theoretically optimal spacing region as shell length increases beyond 40 mm (Figs. 2, 3). Specimens of P. magellanicus 40 to 80 mm in length demonstrate the greatest swimming ability (5); our data strongly suggest that streamwise riblets may be a contributing factor to the swimming success in scallops of this size range.

Body composition and endocrine function in women with acquired immunodeficiency syndrome wasting

The acquired immunodeficiency syndrome (AIDS) wasting syndrome is a devastating complication of human immunodeficiency virus (HIV) infection characterized by progressive weight loss and severe inanition. In men, the wasting syndrome is characterized by a disproportionate decrease in lean body mass and relative fat sparing. In contrast, relatively little is known about the gender-specific changes in body composition that characterize AIDS wasting in women. Three groups of women were studied to determine body composition and hormonal changes with respect to stage of wasting [nonwasting (NW; weight >90% ideal body weight; weight loss <10% of preillness maximum; n = 12), early wasting (EW; weight >90% ideal body weight; weight loss >10% of preillness maximum; n = 10), and late wasting (LW; weight <90%; n = 9)] and compared with a control group of 12, healthy, age-matched women. Weight loss averaged 6 +/- 6% (NW), 15 +/- 6% (EW), and 20 +/- 8% (LW) in the three groups. Lean, fat, and muscle masses were determined by dual energy x-ray absorptiometry and urinary creatinine excretion. Subjects were 36 +/- 5 yr of age (mean +/- SD) with a CD4 cell count of 379 +/- 239 cells/mm3. The body mass index was 24.4 +/- 2.6 kg/m2 (NW), 22.2 +/- 1.2 kg/m2 (EW), 18.2 +/- 2.0 kg/m2 (LW), and 24.3 +/- 2.6 kg/m2 (controls; P < 0.01, NW vs. EW; P < 0.0001, NW vs. LW). Lean body mass indexed for height was 15.7 +/- 2.4 kg/m2 (NW), 14.8 +/- 2.0 kg/m2 (EW), and 13.7 +/- 1.2 kg/m2 (LW) and was decreased significantly only in the LW group (P < 0.05 vs. NW). Muscle mass was 96% (NW), 94% (EW), and 78% (LW) of that predicted for height (P < 0.05, NW vs. LW). In contrast, fat mass indexed for height was decreased significantly among patients in both the EW and LW groups [8.7 +/- 1.9 kg/m2 (NW), 6.5 +/- 1.9 kg/m2 (EW), and 3.7 +/- 1.4 kg/m2 (LW); P < 0.05, NW vs. EW; P < 0.001, NW vs. LW). Expressed as a percentage of the value in nonwasting HIV-positive controls (NW), the relative loss of fat was greater than the loss of lean mass with progressive degrees of wasting [EW, 25% vs. 6% (fat vs. lean); LW, 58% vs. 13%]. The prevalence of amenorrhea was 20% among study subjects [17% (NW), 10% (EW), and 38% (LW)]. The percent predicted muscle mass was significantly lower in subjects with amenorrhea (74 +/- 8%) compared to that in eumenorrheic HIV-positive subjects (94 +/- 4%; P < 0.05). Estradiol levels were lower among subjects with amenorrhea (17.6 +/- 21.8 pg/mL) compared to eumenorrheic HIV-positive (48.9 +/- 33.6 pg/mL) and control (68.3 +/- 47.6 pg/mL) subjects and did not correlate with body composition. Mean free testosterone, but not total testosterone, levels were decreased in subjects with EW and LW compared to those in age-matched healthy controls, but not compared with those in NW [0.9 +/- 0.6 ng/dL (NW), 0.7 +/- 0.4 ng/dL (EW), 0.6 +/- 0.3 ng/dL (LW), and 2.0 +/- 2.4 ng/dL (controls); P < 0.05, EW vs. controls and LW vs. controls] and correlated with muscle mass (r = 0.37; P < 0.05). The percentages of women with free testosterone levels below the age-adjusted normal range were 33% (NW), 50% (EW), and 66% (LW). Dehydroepiandrosterone sulfate levels were also low in the subjects with LW compared to those in the control group [98 +/- 85 microg/dL (NW), 102 +/- 53 microg/dL (EW), 55 +/- 46 microg/dL (LW), and 132 +/- 68 microg/dL (controls); P < 0.05 LW vs. controls] and were correlated highly with free testosterone levels (r = 0.73; P < 0.00001) and also with muscle mass (r = 0.48; P < 0.01). These data demonstrate that women lose significant lean body and muscle mass in the late stages of wasting. However, in contrast to men, women exhibit a progressive and disproportionate decrease in body fat relative to lean body mass at all stages of wasting, consistent with gender-specific effects in body composition in AIDS wasting. (ABSTRACT TRUNCATED)

Occurrence of Cowpea Stunt Disease Causing Viruses on Wild Bean in Arkansas

Cucumber mosaic cucumovirus (CMV) and blackeye cowpea mosaic potyvirus (BlCMV) interact synergistically in dually infected plants to cause cowpea stunt disease (1,2). During a July 1996 survey of cowpea stunt-affected fields in the Arkansas River valley, several wild bean (Strophostyles helvola L. Elliott) plants expressing mosaic symptoms were observed and collected. Sap was extracted from symptomatic leaves and used as inoculum to conduct a host range study. Virus symptoms diagnostic for BlCMV, CMV, or cowpea stunt were observed 6 to 8 days post-inoculation on Vigna unguiculata (L.) Walp. subsp. unguiculata cv. Coronet, while chlorotic lesions and mild systemic mosaic symptoms developed on Nicotiana benthamiana. Enzyme-linked immunosorbent assays (ELISAs) conducted on extracts from symptomatic cowpea and N. benthamiana 14 days after inoculation verified the presence of CMV and BlCMV in single and mixed infections. Additional symptomatic wild bean plants were collected from the same site in October 1996. ELISAs and Ouchterlony gel diffusion assays confirmed the presence of CMV and BlCMV, as well as soybean mosaic potyvirus (SMV), cowpea chlorotic mottle bromovirus, and alfalfa mosaic virus (AlMV) in symptomatic wild bean plants. While some of the collected plants were infected with only one virus, others had combined infections of CMV and BlCMV or these two viruses with AlMV. Interestingly, AlMV isolated from wild bean caused symptoms on greenhouse-grown cowpeas that were as severe or more severe than those caused by the cowpea stunt synergy, often resulting in plant death within 8 to 10 days after inoculation. The SMV from wild bean did not induce symptoms on cowpea and was not detected in extracts from inoculated cowpea plants by Ouchterlony gel diffusion assays, but was able to systemically infect soybean (Glycine max L.) cvs. Bragg and Lee. Another virus known to infect cowpea, southern bean mosaic sobemovirus, was not detected in any of the samples tested. To our knowledge, this is the first report that wild bean can serve as an alternate host for cowpea stunt-causing viruses in single and mixed infections. In addition, these data suggest that AlMV may pose a threat to Arkansas-grown cowpeas. References: (1) E. J. Anderson et al. Ark. Farm Res. 43:14, 1994. (2) G. Pio-Ribeiro et al. Phytopathology 68:1260, 1978.

Increase in bone density and lean body mass during testosterone administration in men with acquired hypogonadism

Acquired hypogonadism is being increasingly recognized in adult men. However, the effects of long term testosterone replacement on bone density and body composition are largely unknown. We investigated 36 adult men with acquired hypogonadism (age, 22-69 yr; median, 58 yr), including 29 men with central hypogonadism and 7 men with primary hypogonadism, and 44 age-matched eugonadal controls. Baseline evaluation included body composition analysis by bioimpedance, determination of site-specific adipose area by dual energy quantitative computed tomography scan (QCT) of the lumbar spine, and measurements of spinal bone mineral density (BMD) using dual energy x-ray absortiometry, spinal trabecular BMD with QCT, and radial BMD with single photon absorptiometry. Percent body fat was significantly greater in the hypogonadal men compared to eugonadal men (mean +/- SEM, 26.4 +/- 1.1% vs. 19.2 +/- 0.8%; P < 0.01). The mean trabecular BMD determined by QCT for the hypogonadal men was 115 +/- 6 mg K2HPO4/cc. Spinal BMD was significantly lower than that in eugonadal controls (1.006 +/- 0.024 vs. 1.109 +/- 0.028 g/cm2; P = 0.02, respectively). Radial BMD was similar in both groups. Testosterone enanthate therapy was initiated in 29 hypogonadal men at a dose of 100 mg/week, and the subjects were evaluated at 6-month intervals for 18 months. During testosterone therapy, the percent body fat decreased 14 +/- 4% (P < 0.001). There was a 13 +/- 4% decrease in subcutaneous fat (P < 0.01) and a 7 +/- 2% increase in lean muscle mass (P = 0.01) during testosterone therapy. Spinal BMD and trabecular BMD increased by 5 +/- 1% (P < 0.001) and 14 +/- 3% (P < 0.001), respectively. Radial BMD did not change. Serum bone-specific alkaline phosphatase and urinary deoxypyridinoline excretion, markers of bone formation and resorption, respectively, decreased significantly over the 18 months (P = 0.003 and P = 0.04, respectively). We conclude that testosterone therapy given to adult men with acquired hypogonadism decreases sc fat and increases lean muscle mass. In addition, testosterone therapy reduces bone remodeling and increases trabecular bone density. The beneficial effects of androgen administration on body composition and bone density may provide additional indications for testosterone therapy in hypogonadal men.

Working memory in chess

Three experiments investigated the role of working memory in various aspects of thinking in chess. Experiment 1 examined the immediate memory for briefly presented chess positions from master games in players from a wide range of abilities, following the imposition of various secondary tasks designed to block separate components of working memory. Suppression of the articulatory loop (by preventing subvocal rehearsal) had no effect on measures of recall, whereas blocking the visuospatial sketchpad (by manipulation of a keypad) and blocking the central executive (by random letter generation) had equivalent disruptive effects, in comparison with a control condition. Experiment 2 investigated the effects of similar secondary tasks on the solution (i.e., move selection) of tactical chess positions, and a similar pattern was found, except that blocking the central executive was much more disruptive than in Experiment 1. Experiment 3 compared performance on two types of primary task, one concerned with solving chess positions as in Experiment 2, and the other a sentence-rearrangement task. The secondary tasks in each case were both designed to block the central executive, but one was verbal (vocal generation of random numbers), while the other was spatial in nature (random generation of keypresses). Performance of the spatial secondary task was affected to a greater extent by the chess primary task than by the verbal primary task, whereas there were no differential effects on these secondary tasks by the verbal primary task. In none of the three experiments were there any differential effects between weak and strong players. These results are interpreted in the context of the working-memory model and previous theories of the nature of cognition in chess.

Amyotrophic lateral sclerosis patients' perspectives on use of mechanical ventilation

Thirteen persons diagnosed with amyotrophic lateral sclerosis were interviewed to determine the factors involved in making a decision whether to use mechanical ventilatory support. All study participants believed that they alone should make the decision regarding use of mechanical ventilation. The factors they considered to be of most importance were quality of life, severity of disability, availability of ventilation by means of a nasal mask, possible admission to a long-term care facility, ability to discontinue use of mechanical ventilation, desire to live, concern for their families' emotional health, and concern for care demands placed on their families. Suggestions are offered to facilitate the patient's decision-making process through provision of more information and improved dialogue between patient and professional.

The diverged copy of the citrus tristeza virus coat protein is expressed in vivo

Nucleotide sequence analysis of a portion of the citrus tristeza closterovirus (CTV) genome revealed an open reading frame immediately upstream of the coat protein gene that can encode a protein with a calculated M(r) of 27,360 (p27). The deduced amino acid sequence indicated that this putative nonstructural gene product is highly homologous to the coat protein. To investigate whether p27 was expressed in CTV-infected plants, a fusion protein of p27 produced in Escherichia coli was used to raise polyclonal antibodies. Western blot analysis using the p27 antibodies indicated that p27 is expressed in CTV-infected citrus, but not in uninfected plants. Tissue fractionation studies revealed that p27 accumulates in cell wall enriched fractions.

Nucleotide sequence and organization of eight 3' open reading frames of the citrus tristeza closterovirus genome

The citrus tristeza closterovirus (CTV) RNA genome was cloned as cDNA generated from both CTV-specific double-stranded RNA and genomic RNA, and the sequence of the 3' 7292 nucleotides was determined. The sequenced portion contained eight open reading frames potentially encoding, in the 5' to 3' direction, proteins with the apparent molecular weights of 65, 61, 27, 25 (capsid protein, CP), 18, 13, 20, and 23 kDa, and a potential noncoding region of 277 nucleotides. The 65-kDa protein is a viral homolog of cellular hsp70 heat shock proteins (hsp), the 61-kDa protein is distantly related to the hsp90 proteins, and the 27-kDa protein is a diverged copy of the CP. Database searches did not identify any protein sequences of significant similarity to the remaining four ORFs downstream of the CP. A specific four-gene module consisting of the hsp70 protein, the hsp90-related protein, the diverged copy of the CP, and the CP itself was found to be common in organization between CTV and beet yellows closterovirus. All four proteins in this module were highly conserved, indicating that these viruses probably have evolved from a common ancestor.

PEERing into the past--trends documented in the performance efficiency evaluation report

PEER--the performance efficiency evaluation report--is a quarterly data reporting service produced by CRAHCA. Authors Eric J. Anderson and David N. Gans, MHA, explain how PEER was utilized to discover whether capitated HMO groups achieved higher revenues with lower utilization than non-prepaid groups.

Identification of domains within gene VI of cauliflower mosaic virus that influence systemic infection of Nicotiana bigelovii in a light-dependent manner

Gene VI of cauliflower mosaic virus strains D4 and W260 is an important determinant of systemic infection in solanaceous species (Qiu and Schoelz, 1992). To investigate whether D4 and W260 share any sequences within gene VI that determine their solanaceous host range, we characterized more completely the regions of gene VI involved in systemic infection of Nicotiana bigelovii. We found that two domains within gene VI, which corresponded approximately to the 5' third and middle third of gene VI, influenced systemic infection of N. bigelovii. Exchange of these domains between D4, W260, and CaMV strain CM1841, a strain which is unable to systemically infect any solanaceous plant, revealed different virus combinations that could specify systemic infection of N. bigelovii when plants were grown under two different lighting conditions. Systemic infection of N. bigelovii by D4/CM1841 chimeric viruses required only the 5' third (domain 1) of gene VI of D4. In contrast, systemic infection of N. bigelovii by W260/CM1841 chimeric viruses required both the domain 1 and middle third of gene VI (domain 2) of W260, as well as two other regions primarily containing W260 genes I and II, and gene IV. The genetic requirements for systemic infection by chimeric viruses were not as stringent when plants were grown under low light conditions. Specifically, domain 2 of gene VI of D4 contained sequences sufficient for D4/CM1841 chimeric viruses to systemically infect N. bigelovii at low light intensity. We sequenced gene VI of strain W260 and compared differences in the deduced amino acid sequences between W260 and the previously published sequences of D4 and CM1841. There was only one amino acid position in domain 1 of gene VI, and no sites in domain 2, in which W260 and D4 agreed with each other and differed from CM1841. Consequently, the host range studies and sequence information indicate that different sequences within gene VI of CaMV strains W260 and D4 are responsible for systemic infection of N. bigelovii.