Inflammatory biomarkers in dentinal fluid as an approach to molecular diagnostics in pulpitis

AIM

To explore a set of inflammatory biomarkers obtained from dentinal fluid (DF) from patients with symptomatic irreversible pulpitis (IP), reversible pulpitis (RP) and normal pulp (NP).

METHODOLOGY

A cross-sectional exploratory study was performed, recruiting 64 patients on the basis of their respective pulp condition. DF samples were obtained from all patients (23, from IP patients; 20, from RP patients; and 21, from NP patients). Quantification of biomarkers was performed using a Luminex® MAGPIX platform system and multiplex assay kits. The Kruskal-Wallis test was used for comparisons with regard to pulp state. A simple logistic regression model and the odds ratio (OR) with a 95% level of confidence (P = 0.05) were used to evaluate associations between biomarker levels and pulpal diagnosis. The performance discrimination of the biomarkers was evaluated through the construction of a receiver operating characteristic (ROC) curve by calculating the area under the curve (AUC) for IP versus RP after logistic regression modelling. Youden criteria were used to establish cut-off points for biomarkers alone with AUC > 70 and P-value < 0.05, or estimated probabilities from the multivariable logistic model.

RESULTS

The biomarkers that had significantly higher values in participants with IP versus RP were IL-1α, VEGF-α and FGF acid (P < 0.05). FGF acid (OR: 12.62; P = 0.0085; CI 95% 1.91-83.29) and VEGF-α (OR: 2.61; P = 0.0252; CI 95% 1.13-6.03) were associated with pulp diagnoses of IP versus RP. The AUC-ROC curve for FGF acid was 0.79. The model containing FGF acid, IL-1α, IL-6 and TIMP-1 had an AUC-ROC of 0.92 for IP versus RP with a significant difference from the FGF acid ROC curve (P = 0.0231).

CONCLUSIONS

Dentinal fluid could be used to assay pulpal mediators in the molecular diagnosis of pulpitis. Despite the limitation of the clinical diagnostics used in the present study, it was possible to detect a difference between irreversible symptomatic pulpitis and reversible pulpitis associated with the following combined biomarkers: FGF acid + IL-6 + IL-1α, +TIMP-1.

Effect of perfluorodecanoic acid on pig oocyte viability, intracellular calcium levels and gap junction intercellular communication during oocyte maturation in vitro

Perfluorodecanoic acid (PFDA) is a synthetic perfluorinated compound, which has been reported to exert adverse effects on somatic cells. However, its effects on germ cells have not been studied to date. The aim of the present study was to analyze the effects of PFDA on the viability, intracellular calcium levels and gap junction intercellular communication (GJIC) during porcine oocyte maturation in vitro. PFDA negatively impacted oocyte viability (medium lethal concentration, LC₅₀ = 7.8 μM) and maturation (medium inhibition of maturation, IM₅₀ = 3.8 μM). Oocytes exposed to 3.8 μM PFDA showed higher levels of intracellular calcium relative to control oocytes. In addition, GJIC among the cumulus cells and the oocyte was disrupted. The effects of PFDA on oocyte calcium homeostasis and intercellular communication seem to be responsible for the inhibition of oocyte maturation and oocyte death. In addition, since the deleterious effects of PFDA on oocyte viability, maturation and GJIC are significantly stronger than the previously reported effects of another widely used perfluorinated compound (Perfluorooctane sulfonate) in the same model, the use of PFDA in consumer products is questioned.

IFPA meeting 2015 workshop report II: mechanistic role of the placenta in fetal programming; biomarkers of placental function and complications of pregnancy

Workshops are an integral component of the annual International Federation of Placenta Association (IFPA) meeting, allowing for networking and focused discussion related to specialized topics on the placenta. At the 2015 IFPA meeting (Brisbane, Australia) twelve themed workshops were held, three of which are summarized in this report. These workshops focused on various aspects of placental function, particularly in cases of placenta-mediated disease. Collectively, these inter-connected workshops highlighted the role of the placenta in fetal programming, the use of various biomarkers to monitor placental function across pregnancy, and the clinical impact of novel diagnostic and surveillance modalities in instances of late onset fetal growth restriction (FGR).

Texting while driving: is speech-based text entry less risky than handheld text entry?

Research indicates that using a cell phone to talk or text while maneuvering a vehicle impairs driving performance. However, few published studies directly compare the distracting effects of texting using a hands-free (i.e., speech-based interface) versus handheld cell phone, which is an important issue for legislation, automotive interface design and driving safety training. This study compared the effect of speech-based versus handheld text entries on simulated driving performance by asking participants to perform a car following task while controlling the duration of a secondary text-entry task. Results showed that both speech-based and handheld text entries impaired driving performance relative to the drive-only condition by causing more variation in speed and lane position. Handheld text entry also increased the brake response time and increased variation in headway distance. Text entry using a speech-based cell phone was less detrimental to driving performance than handheld text entry. Nevertheless, the speech-based text entry task still significantly impaired driving compared to the drive-only condition. These results suggest that speech-based text entry disrupts driving, but reduces the level of performance interference compared to text entry with a handheld device. In addition, the difference in the distraction effect caused by speech-based and handheld text entry is not simply due to the difference in task duration.

Porphyromonas gingivalis, Treponema denticola and toll-like receptor 2 are associated with hypertensive disorders in placental tissue: a case-control study

AIM(S)

To explore the associations between the presence of periodontal pathogens and the expression of toll-like receptors (TLR-2 and TLR-4) in the placental tissue of patients with hypertensive disorders compared to the placentas of healthy normotensive patients.

MATERIAL AND METHODS

A case-control study was performed. From a cohort composed of 126 pregnant women, 33 normotensive healthy pregnant women were randomly selected, and 25 cases of patients with hypertensive disorders of pregnancy, including gestational hypertension and pre-eclampsia, were selected. Placental biopsy was obtained after aseptic placental collection at the time of delivery. All of the samples were processed and analysed for the detection of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Treponema denticola and Tannerella forsythia using the polymerase chain reaction (PCR) technique. Determination of the expressions of TLR-2 and TLR-4 was performed in samples of total purified protein isolated from placental tissues and analysed by ELISA. The data were assessed using descriptive statistics. The associations among variables were estimated through multiple logistic regression models and the Mann-Whitney test to evaluate the differences between the two groups.

RESULTS

A significant increase was observed in the expression of TLR-2 in the placentas of patients with hypertensive disorders (p = 0.04). Additionally, the multiple logistic regression models demonstrated an association between the presence of T. denticola and P. gingivalis in placental tissues and hypertensive disorders (OR: 9.39, p = 0.001, CI 95% 2.39-36.88 and OR: 7.59, p = 0.019, CI 95% 1.39-41.51, respectively).

CONCLUSIONS

In the present study, pregnant women with periodontal disease presented an association in the placental tissue between the presence of T. denticola and P. gingivalis and hypertensive disorders. Additionally, increased expression of TLR-2 was observed. However, further studies are required to determine the specific roles of periodontal pathogens and TLRs in the placental tissue of patients with pregnancy-related hypertensive disorders.

Increased inflammatory biomarkers in early pregnancy is associated with the development of pre-eclampsia in patients with periodontitis: a case control study

AIM(S)

To explore the relationship between biomarkers of systemic inflammation in plasma and gingival crevicular fluid in early pregnancy and the subsequent development of pre-eclampsia in patients with periodontitis.

MATERIALS AND METHODS

A case-control study was performed. From a cohort composed of 126 pregnant women, 43 normotensive healthy pregnant women were randomly selected, and 11 cases of preeclampsia were identified. Plasmatic and gingival crevicular fluid (GCF) samples were collected in early pregnancy (11-14 wk gestation). The levels of interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) were measured in the plasma and GCF samples, whereas the level of C-reactive protein (CRP) was measured in plasma samples. Biomarkers were determined by ELISA assays. The data were analysed using descriptive statistics, and the association between variables was estimated through logistic regression models.

RESULTS

There was observed an association between pre-eclampsia and plasmatic levels of CRP (OR: 1.07; p = 0.003). Additionally, pre-eclampsia also was associated with IL-6 levels in GCF samples in early pregnancy (OR: 1.05; p = 0.039). A multiple logistic regression model suggests that increased levels of IL-6 in GCF (OR = 1.06; p = 0.02; CI 95% 1.007-1.117) in early pregnancy increase the risk of developing pre-eclampsia.

CONCLUSION(S)

Pregnant women with periodontitis who later development pre-eclampsia, shows increased levels of IL-6 in GCF and CRP in plasma during early pregnancy. Periodontal disease could contribute to systemic inflammation in early pregnancy via a local increase of IL-6 and the systemic elevation of CRP. Therefore, both inflammatory markers could be involved in the relationship between periodontal disease and pre-eclampsia.

Stimulatory response of neutrophils from periodontitis patients with periodontal pathogens

OBJECTIVE

Neutrophils play a crucial role in the defense of invading bacteria by releasing biologically active molecules. The response of peripheral blood neutrophils was studied in periodontitis-affected patients and in healthy controls towards stimulation to Porphyromonas gingivalis (Pg) and Actinobacillus actinomycetemcomitans (Aa) extracts.

MATERIALS AND METHODS

Peripheral venous blood was drawn from 23 adult patients with moderate to advanced chronic periodontitis (probing depth >or=5 mm, attachment loss >or=3 mm), and 30 healthy volunteers. Neutrophil response followed by metalloproteinase-9 (MMP-9) and interleukin-8 (IL-8) secretion was assayed by zymography and enzyme-linked immunosorbent assay, respectively, on both whole blood and purified neutrophils. In addition to periodontal pathogen extracts, known stimulating agents were tested, such as Escherichia coli-lipopolysaccharide (LPS), phytohemagglutinin, and zymosan A.

RESULTS

Neutrophil response, expressed as a secretion ratio under stimulated and non-stimulated conditions, measured in whole blood, showed no differences between periodontitis and healthy controls. Instead, in purified neutrophils from patients, MMP-9 exhibited a significantly higher secretion ratio with LPS and Pg (1.5- to 2-fold), whereas IL-8 showed a larger increase in secretion ratio (3- to 7-fold) in the presence of Pg, Aa, LPS, and zymosan A.

CONCLUSION

Peripheral neutrophils of periodontitis-affected patients are more reactive as suggested by their significantly higher response toward periodontal pathogen extracts and other stimulating agents.

RANKL in human periapical granuloma: possible involvement in periapical bone destruction

OBJECTIVES

The cytokine receptor activator of nuclear factor kappaB-ligand (RANKL) has been involved in both the physiological and pathological regulation of osteoclast life span and bone metabolism. Periapical granuloma is a periradicular lesion characterized by periapical bone destruction. The aims of this study were to associate the RANKL mRNA levels to periapical granulomas using the real-time reverse transcriptase-polymerase chain reaction (RT-PCR) technique and to determine the specific cell involved in RANKL synthesis.

METHODS

In eight periapical granuloma and eight periodontal ligament samples from periodontally healthy volunteers, RANKL mRNA was detected by real-time RT-PCR. Expression of RANKL on infiltrate leukocytes was further investigated by flow cytometry in six periapical granulomas.

RESULTS

Receptor activator of nuclear factor kappaB-ligand mRNA levels were higher in periapical granulomas than in healthy periodontal ligament as its RANKL mRNA cycle threshold (Ct) and DeltaCt were significantly lower than that of controls (33.07 +/- 1.24 vs 36.96 +/- 1.69 and 11.58 +/- 3.02 vs 15.60 +/- 3.31, respectively). A 16.2-fold (2.0-131.6) higher RANKL gene expression was detected in the granulomas compared with the control tissues. We determined by flow cytometry that lymphocytes were the predominant leukocyte cells (53.31%), and monocytes and dendritic cells were the main RANKL synthesizers in granuloma lesions.

CONCLUSIONS

These data indicate that monocytes synthesized RANKL in periapical granulomas and suggest that RANKL is involved in bone loss associated with periapical lesions.

Transbronchial administration of adenoviral-mediated interleukin-10 gene to the donor improves function in a pig lung transplant model

Interleukin-10 (IL-10) gene transfection of donor lungs prior to transplantation is an attractive strategy to reduce ischemia-reperfusion induced lung injury. However, experimental data with gene therapy in large animal models of lung transplantation are generally lacking. We have developed a simple clinically applicable technique for adenoviral-mediated gene delivery of human IL-10 to the lung of large animals that provides homogenous gene expression after 12-24 h of transfection. Using this technique of gene delivery, we have studied the dynamics of adenoviral gene delivery to the lung in the setting of lung transplantation. Although there is a persistent inflammatory response to the adenoviral vector, we achieved significant expression of human IL-10 in lung tissue before lung retrieval to obviate the deleterious impact of the adenoviral vector on the donor lung. The administration of adenoviral-mediated human IL-10 to the donor lung reduced ischemia-reperfusion injury and improved graft function after lung transplantation in this pig lung transplantation model. Transfection of adenoviral-mediated human IL-10 to the donor lung prevented the release of inflammatory cytokines such as IL-6 in lung tissue and plasma. We have demonstrated that IL-10 gene therapy has significant potential to prevent or treat the inflammatory response associated with ischemia-reperfusion injury in lung transplantation. In the future, IL-10 gene therapy could also be used for immunomodulation or tolerance induction.

Range of motion of the wrist: implications for designing computer input devices for the elderly

PURPOSE

The purpose of this study was to report normative values of the amplitude of joint wrist motions and grip strength for older age groups.

METHOD

Volunteers. (N = 147) were divided into four age groups, 60-69, 70-79, 80-89 and 90+ years, with a total of 62 men and 85 women. Maximum range motion values were obtained for wrist flexion, extension and ulnar deviation. In addition, grip strength measures were obtained for each participant.

RESULTS

In general, the strength and ROM values for the oldest participants in this study were lower than those of the younger age group (age 60 to 69) and significantly lower than those published for subjects between 25 and 54 years of age. Furthermore, across all age groups males were significantly stronger than females. However, females tended to have greater ROM than males, particularly for wrist extension and ulnar deviations. Joint ROM and grip strength declined significantly with age for both males and females. Comparisons with published data for younger subjects (age 25-35) indicate that a 60-69 year old male, will on average experience a decline in wrist flexion, extension and ulnar deviation of 12%, 41%, and 22% respectively. By age 90, an individual may be expected to have ROM values that are only approximately 60% of an average 30 year old individual.

CONCLUSION

The results suggest that the ageing population (particularly men) may face greater difficulty using an input device such as a mouse that relies on motions of the wrist. In addition, the reduced ROM of the wrist may put the elderly at greater risk of developing cumulative trauma disorders. The implications of these findings for the design of input devices are discussed.

Colour adaptation modifies the temporal properties of the long- and middle-wave cone signals in the human luminance mechanism

The human luminance mechanism (LUM) detects rapid flicker and motion, summating the neurally integrated L' and M' 'contrast' signals from the long- and middle-wave cones, respectively. We previously observed large temporal phase shifts between the L' and M' signals in LUM, which were maximal and of reversed sign on green versus orange background fields and which were accompanied by large variations in the relative L' and M' contrast weights. The effects were modelled with phasic magnocellar retinal ganglion cells. The changing L' versus M' contrast weights in the model predict that the temporal dynamics of the L' and M' luminance signals will differ on green and orange fields. This is assessed with several protocols. Motion thresholds for 1 cycle deg(-1) drifting gratings or static pulsed gratings on the orange field show that the M' signal is more temporally bandpass than the L' signal; this reverses on the green field. Strong motion due to the different dynamics of the L' and M' signals is even seen with a pair of L' and M' gratings pulsed simultaneously. Impulse response functions were measured with gratings pulsed spatially in phase or antiphase. The impulse response was clearly biphasic for the M' signal on the orange field and L' signal on the green field, while the other signals were more sustained. The impulse responses predicted the motion seen with gratings pulsed in spatial quadrature.

Targeting of the soybean leghemoglobin to tobacco chloroplasts: effects on aerobic metabolism in transgenic plants

Several attempts have been made to alter the aerobic metabolism of plants, especially those related to the oxygenation or carboxylation of Rubisco. However, designing a more efficient Rubisco protein is rather problematic since its structural manipulation leads frequently to an enhancement of oxygenase activity, which is responsible for photorespiratory losses. In order to reduce oxygen availability inside the chloroplast, a chimeric gene consisting of a soybean leghemoglobin cDNA (lba) ligated to the chloroplast targeting signal sequence of the Rubisco small subunit gene, was introduced and expressed in Nicotiana tabacum. Lb was efficiently imported and correctly processed inside the chloroplasts of transgenic tobacco plants. Furthermore, the level of Lb expression in leaf tissue ranged from 0.01 to 0.1%. Analysis of photosynthesis, starch, sucrose and enzymes involved in aerobic metabolism, revealed that despite the high affinity of Lb for oxygen, no significant difference was observed in relation to the control plants. These results suggest that higher Lb concentrations would be required inside the chloroplasts in order to interfere on aerobic metabolism.

Second-site adaptation in the red-green detection pathway: only elicited by low-spatial-frequency test stimuli

The red-green (RG) detection mechanism was revealed by measuring threshold detection contours in the L and M cone contrast plane for sine-wave test gratings of 0.8-6 c deg-1 on bright adapting fields of yellow or red. The slope of the RG detection contours was unity, indicating that the L and M contrast signals contribute equally (with opposite signs) on both the yellow and the red fields: this reflects first-site, cone-selective adaptation. Second-site adaptation, which may reflect saturation at a color-opponent site, was evidenced by the RG detection contours being further out from the origin of the cone contrast plane on the red field than on the yellow field. Second-site adaptation was strong (3-fold) for low spatial frequency test gratings but greatly diminished by 6 c deg-1. The disappearance of second-site adaptation with increasing spatial frequency can be explained by spatial frequency channels. The most sensitive detectors may comprise a low spatial frequency channel which is susceptible to masking by the chromatic, spatial DC component of the red field. The 6 c deg-1 patterns may be detected by a less sensitive, higher frequency channel which is less affected by the uniform red field. The RG spatial frequency channels likely arise in the cortex, implicating a partially central site for the second-site effect.

Spatial masking does not reveal mechanisms selective to combined luminance and red-green color

Detection thresholds plotted in the L and M cone-contrast plane have shown that there are two primary detection mechanisms, a red-green hue mechanism and a light-dark luminance mechanism. However, previous masking results suggest there may be additional mechanisms, responsive to combined features like bright and red or dark and green. We measured detection thresholds for a 1.2 c deg-1 sine-wave grating in the presence of a spatially matched mask grating which was either stationary, dynamically jittered or flickered. The stimuli could be set to any direction in the L,M plane. The appearance of selectivity for combined hue and luminance arose only in conditions where adding the test to the mask modified the spatial phase offset between the luminance and red-green stimulus components. Sensitivity was very high for detecting this spatial phase offset. When this extra cue was eliminated, masking contours in the L,M plane could be largely described by the classical red-green and luminance mechanisms.

Motion detection on flashed, stationary pedestal gratings: evidence for an opponent-motion mechanism

Contrast thresholds were measured for discriminating left vs right motion of a vertical, 1 c/deg luminance grating lasting for one cycle of motion. This test was presented on a 1 c/deg stationary grating (pedestal) of twice-threshold, flashed for the duration of the test motion. Lu and Sperling [(1995). Vision Research, 35, 2697-2722] argue that the visual system detects the underlying, first-order motion of the test and is immune to the presence of the stationary pedestal (and the 'feature wobble' which it induces). On the contrary, we observe that the stationary pedestal has large effects on motion detection at 7 and 15 Hz, and smaller effects at 0.9-3.7 Hz, evidenced by a spatial phase dependency between the stationary pedestal and moving test. At 15 Hz the motion threshold drops as much as five-fold, with the stationary pedestal in the optimal spatial phase (i.e., pedestal and test spatially in phase at middle of motion), and the perceived direction of the test motion reverses with the pedestal in the opposite phase. Phase dependency was also explored using a very brief (approximately 1 msec) static pedestal presented with the moving test. The pedestal of Lu and Sperling (flashed for the duration of the test) has a broad spectrum of left and right moving components which interact with the moving test. The pedestal effects can be explained by the visual system's much higher sensitivity to the difference of the contrast of right vs left moving components than to either component alone.

Short-wave cone signal in the red-green detection mechanism

Previous work shows that the red-green (RG) detection mechanism is highly sensitive, responding to equal and opposite long-wave (L) and middle-wave (M) cone contrast signals. This mechanism mediates red-green hue judgements under many conditions. We show that the RG detection mechanism also receives a weak input from the short-wave (S) cones that supports the L signal and equally opposes M. This was demonstrated with a pedestal paradigm, in which weak S cone flicker facilitates discrimination and detection of red-green flicker. Also, a near-threshold +S cone flash facilitates detection of red flashes and inhibits green flashes, and a near-threshold -S cone flash facilitates detection of green flashes and inhibits red flashes. The S contrast weight in RG is small relative to the L and M contrast weights. However, a comparison of our results with other studies suggests that the strength of the absolute S cone contrast contribution to the RG detection mechanism is 1/4 to 1/3 the strength of the S contribution to the blue-yellow (BY) detection mechanism. Thus, the S weight in RG is a significant fraction of the S weight in BY. This has important implications for the 'cardinal' color mechanisms, for it predicts that for detection or discrimination, the mechanisms limiting performance do not lie on orthogonal M-L and S axes within the equiluminant color plane.

Colour adaptation modifies the long-wave versus middle-wave cone weights and temporal phases in human luminance (but not red-green) mechanism

1. The human luminance (LUM) mechanism detects rapid flicker and motion, responding to a linear sum of contrast signals, L' and M', from the long-wave (L) and middle-wave (M) cones. The red-green mechanism detects hue variations, responding to a linear difference of L' and M' contrast signals. 2. The two detection mechanisms were isolated to assess how chromatic adaptation affects summation of L' and M' signals in each mechanism. On coloured background (from blue to red), we measured, as a function of temporal frequency, both the relative temporal phase of the L' and M' signals producing optimal summation and the relative L' and M' contrast weights of the signals (at the optimal phase for summation). 3. Within the red-green mechanism at 6 Hz, the phase shift between the L' and M' signals was negligible on each coloured field, and the L' and M' contrast weights were equal and of opposite sign. 4. Relative phase shifts between the L' and M' signals in the LUM mechanism were markedly affected by adapting field colour. For stimuli of 1 cycle deg-1 and 9 Hz, the temporal phase shift was zero on a green-yellow field (approximately 570 nm). On an orange field, the L' signal lagged M' by as much as 70 deg phase while on a green field M' lagged L' by as much as 70 deg. The asymmetric phase shift about yellow adaptation reveals a spectrally opponent process which controls the phase shift. The phase shift occurs at an early site, for colour adaptation of the other eye had no effect, and the phase shift measured monocularly was identical for flicker and motion, thus occurring before the motion signal is extracted (this requires an extra delay). 5. The L' versus M' phase shift in the LUM mechanism was generally greatest at intermediate temporal frequencies (4-12 Hz) and was small at high frequencies (20-25 Hz). The phase shift was greatest at low spatial frequencies and strongly reduced at high spatial frequencies (5 cycle deg-1), indicating that the receptive field surround of neurones is important for the phase shift. 6. These temporal phase shifts were confirmed by measuring motion contrast thresholds for drifting L cone and M cone gratings summed in different spatial phases. Owing to the large phase shifts on green or orange fields, the L and M components were detected about equally well by the LUM mechanism (at 1 cycle deg-1 and 9 Hz) when summed spatially in phase or in antiphase. Antiphase summation is typically thought to produce an equiluminant red-green grating. 7. At low spatial frequency, the relative L' and M' contrast weights in the LUM mechanism (assessed at the optimal phase for summation) changed strongly with field colour and temporal frequency. 8. The phase shifts and changing contrast weights were modelled with phasic retinal ganglion cells, with chromatic adaptation strongly modifying the receptive field surround. The cells summate L' and M' in their centre, while the surround L' and M' signals are both antagonistic to the centre for approximately 570 nm yellow adaptation. Green or orange adaptation is assumed to modify the L and M surround inputs, causing them to be opponent with respect to each other, but with reversed polarity on the green versus orange field (to explain the chromatic reversal of the phase shift). Large changes in the relative L' and M' weights on green versus orange fields indicate the clear presence of the spectrally opponent surround even at 20 Hz. The spectrally opponent surround appears sluggish, with a long delay (approximately 20 ms) relative to the centre.

Prevalence of malnutrition in Mexican CAPD diabetic and nondiabetic patients

Malnutrition is often present on continuous ambulatory peritoneal dialysis (CAPD), and contributes to morbidity and mortality. Diabetics (DM) have an increased risk for developing malnutrition. Our purpose was to assess the nutritional status (NS) of our CAPD population, to define NS differences between DM and nondiabetics (NoDM), and to identify NS-related factors. Patients were subjected to a nutritional assessment, which included a 24-hour dietary recall and a nutritional scoring system including anthropometric, biochemical, and subjective evaluation, and that classifies patients as: normal, and mildly, moderately, and severely malnourished. We studied 90 patients: 35 DM and 55 NoDM. In our whole population we observed a high frequency of malnutrition: NS was normal in 18%, and 20% had mild, 24% had moderate, and 38% had severe malnutrition. Ninety-one percent of DM and 76% of NoDM showed some degree of malnutrition. DM patients had significantly higher levels of malnutrition (p = 0.02), were significantly older, had more body fat, and spent less time on dialysis. There were 37 males and 53 females. Sex distribution was similar between DM and NoDM. Seventy-six percent of males and 86% of females had malnutrition. Moderate and severe malnourishment were more frequent in females. DM and female sex were the strongest predictors for moderate and severe malnutrition.

Human cones appear to adapt at low light levels: measurements on the red-green detection mechanism

Recent physiological evidence suggests that cones do not light adapt at low light levels. To assess whether adaptation is cone-selective at low light levels, the red-green detection mechanism was isolated. Thresholds were measured with a large test flash, which stimulated the L and M cones in different fixed amplitude ratios, on different colored adapting fields. Thresholds were plotted in L and M cone contrast coordinates. The red-green mechanism responded to an equally-weighted difference of L and M cone contrast on each colored field, demonstrating equivalent, Weberian adaptation of the L and M cone signals. The L and M cone signals independently adapted for illuminance levels as low as 60 effective trolands (e.g. M-cone trolands). Since this adaptation is entirely selective to cone type, it suggests that the cones themselves light-adapt. The red-green detection contour on reddish fields was displaced further out from the origin of the cone contrast coordinates, revealing an additional sensitivity loss at a subsequent, spectrally-opponent site. This second-site effect may arise from a net "red" or "green" signal that represents the degree to which the L and M cones are differently hyperpolarized by the steady, colored adapting field. Such differential hyperpolarization is compatible with equivalent, Weberian adaptation of the L and M cones.

Contributions of human long-wave and middle-wave cones to motion detection

1. It has been suggested that motion may be best detected by the luminance mechanism. If this is the most sensitive mechanism, motion thresholds may be used to isolate the luminance mechanism and study its properties. 2. A moving (1 cycle deg-1), vertical, heterochromatic (red-plus-green), foveal grating was presented on a bright yellow (577 nm wavelength) field. Detection and motion (direction identification: left versus right) thresholds were measured for different amplitude ratios of the red and green components spatially summed in phase or in antiphase. Threshold contours plotted in cone-contrast co-ordinates (L',M') for the long-wave (L) and middle-wave (M) cones, revealed two motion mechanisms: a luminance mechanism that responds to a weighted sum of L and M contrasts, and a spectrally opponent mechanism that responds to a weighted difference. 3. Detection and motion thresholds, measured at 1-4 Hz, were identical for luminance gratings, having equal cone contrasts, L' and M', of the same sign. For chromatic gratings, with L' and M' of opposite sign, motion thresholds were higher than detection thresholds. A red-green hue mechanism may mediate chromatic detection, and a separate spectrally opponent motion mechanism may mediate motion. 4. The red-green hue mechanism was assessed from 1 to 15 Hz with an explicit hue criterion. The detection contour had a constant slope of one, implying equal L' and M' contributions of opposite sign. For motion identification, L' and M' contributed equally at 1 Hz, but the M' contribution was attenuated at higher velocities. 5. The cone-contrast metric provides a physiologically relevant comparison of sensitivities of the two motion mechanisms. At 1 Hz, the spectrally opponent motion mechanism is approximately 4 times more sensitive than the luminance mechanism. As temporal frequency is increased, the relative sensitivities change so that the luminance mechanism is more sensitive above 9 Hz. 6. The less sensitive motion mechanism was isolated with a quadrature phase protocol, using a pair of heterochromatic red-plus-green gratings, counterphase flickering in spatial and temporal quadrature phase with respect to each other. One grating was set slightly suprathreshold and oriented in cone contrast (L',M') so as to potentiate a single motion mechanism, the sensitivity of which was probed with the second grating, which was varied in (L',M'). This allowed us to measure the motion detection contour of the less sensitive luminance mechanism at low velocities.(ABSTRACT TRUNCATED AT 400 WORDS)

Separable red-green and luminance detectors for small flashes

Detection contours were measured in L and M cone contrast coordinates for foveal flashes of 200 msec duration and 2.3, 5, 10 and 15 min arc diameter on a bright yellow field. The test flash consisted of simultaneous incremental and decremental red and green lights in various amplitude ratios. At all sizes, the most sensitive detection mechanism was not a luminance mechanism, but rather a red-green mechanism that responds to the linear difference of equally weighted L and M cone contrasts, and signals red or green sensations at the detection threshold. Both temporal and spatial integration were greater for red-green detection than luminance detection. A coincident, subthreshold, yellow flash (a luminance pedestal) did not affect the threshold of the red-green mechanism. Such a pedestal is a sum of equal L and M cone contrast--it represents a vector parallel to the red-green detection contour and thus is expected not to stimulate directly the red-green mechanism. When suprathreshold, the coincident pedestal facilitated chromatic detection by approximately 2x at all tested sizes; intense pedestals did not mask chromatic detection. This insensitivity to intense luminance pedestals further indicates that the red-green mechanism has fixed spectral tuning with balanced opponent L and M contrast inputs. This view of fixed spectral weights contrasts with the "variable tuning hypothesis", which postulates that the weights change with spatial-temporal variations in the test stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Reading with rods: the superiority of central vision for rapid reading

PURPOSE

To investigate why the central portion of the visual field is normally the optimal region for pattern recognition.

METHOD

The study uses a reading paradigm in which the text can only be seen with rod vision. Reading rates were measured as the text was positioned in different parts of the visual field.

RESULTS

Observers obtained the highest reading rates when rod-generated images were viewed at or near the fovea.

CONCLUSION

The superiority of the central field for reading is neither linked to some exclusive property of the cone visual system, nor is it primarily related to visual sensitivity or spatiotemporal resolution. The superiority of reading in the central field is associated with some aspect of the visual cortical processes.

Colour is what the eye sees best

It has been argued by Watson, Barlow and Robson that the visual stimulus that humans detect best specifies the spatial-temporal structure of the receptive field of the most sensitive visual neurons. To investigate 'what the eye sees best' they used stimuli that varied in luminance alone. Because the most abundant primate retinal ganglion cells, the P cells, are colour-opponent, we might expect that a coloured pattern would also be detected well. We generalized Watson et al.'s study to include variations in colour as well as luminance. We report here that our best detected coloured stimulus was seen 5-9-fold better than our best luminance spot and 3-8-fold better than Watson's best luminance stimulus. The high sensitivity to colour is consistent with the prevalence and high colour contrast-gain of retinal P cells, and may compensate for the low chromatic contrasts typically found in natural scenes.

Oscillatory potentials of X-linked carriers of congenital stationary night blindness

ERG oscillatory potentials (OPs) were recorded from obligate carriers of CSNB and from age-matched normal subjects. The OPs were recorded under four stimulus conditions and were analyzed in the time and frequency domains. The results, first of all, provide confirmation of the previous report that the OP amplitude is reduced in carriers. Second, the results show that, of four stimulus conditions examined, the best condition for discriminating the carriers and normal subjects was when the flash was blue and the eye was dark-adapted. Third, the results show that, in the frequency domain, optimal discrimination occurs when examining the power content of the OP at a center frequency of about 130 Hz using a 70 Hz bandwidth window. In the time domain, optimal discrimination occurs when examining the amplitude of the third peak of the response.

Reading with the rod visual system

Using the scanned text technique developed by Legge and his colleagues, the present study demonstrates that visually normal subjects can read with the isolated rod visual system. The subjects were able to read text (albeit slowly) at luminances near their absolute thresholds. The peak reading rates increase with luminance at about 40 words per minute for every tenfold increase in luminance. The authors suggest that the study of scotopic reading performance in normal subjects might contribute to an understanding of reading problems in patients with bilateral central scotoma.

Studies on the regulation of assimilatory nitrate reductase in Ankistrodesmus braunii

In the green alga Ankistrodesmus braunii, all the activities associated with the nitrate reductase complex (i.e., NAD(P)H-nitrate reductase, NAD(P)H-cytochrome c reductase and FMNH2-or MVH-nitrate reductase) are nutritionally repressed by ammonia or methylamine. Besides, ammonia or methylamine promote in vivo the reversible inactivation of nitrate reductase, but not of NAD(P)H-cytochrome c reductase. Subsequent removal of the inactivating agent from the medium causes reactivation of the inactive enzyme. Menadione has a striking stimulation on the in vivo reactivation of the inactive enzyme. The nitrate reductase activities, but not the diaphorase activity, can be inactivated in vitro by preincubating a partially purified enzyme preparation with NADH or NADPH. ADP, in the presence of Mg(2+), presents a cooperative effect with NADH in the in vitro inactivation of nitrate reductase. This effect appears to be maximum at a concentration of ADP equimolecular with that of NADH.