Impact of the first Covid-19 pandemic wave on first episode psychosis in Milan, italy

The ongoing Corona Virus Disease 2019 (COVID-19) pandemic appears to increase risk for mental illness, either directly due to inflammation caused by the virus or indirectly due to related psychosocial stress, resulting in the development of both anxious-depressive and psychotic symptoms. The purpose of the present study was to assess the frequency and characteristics of all patients with First Episodes Psychosis (FEP) without COVID-19 infection hospitalized in the first four months since lockdown in Milan. We recruited sixty-two patients hospitalized between March 8 to July 8, 2020 versus those first  hospitalized in the same period in 2019. The two subgroups were compared for sociodemographic variables and clinical characteristics of the episodes. Patients with FEP in 2020 were significantly older than patients with FEP in 2021, and presented with significantly less substances abuse. Interestingly, patients presenting with FEP in 2020 were significantly older than patients with FEP in 2019. These data are compatible with the greater vulnerability to stressful factors during the pandemic, as well as with the greater concern regarding a possible COVID-19 infection producing brain damage causing the FEP.

Clinical outcome and olanzapine plasma levels in acute schizophrenia

Purpose

This open label study was performed to evaluate the relationship between the plasma concentration of olanzapine and the response in acute schizophrenic inpatients.

Material and methods

A total of 54 inpatients, 38 males and 16 females, age ranging from 18 to 75 years, affected by Schizophrenia (DSM IV criteria) during an exacerbation phase were included in the study. Olanzapine (OLZ) was started at a dose of 5–20 mg/day and was increased to a mean dose of 15.27 mg ±5.53 S.D. Patients were evaluated at baseline, and after 2 weeks, by using BPRS, PANNS, HRS-D, EPSE, and ACS.

Results

BPRS and total PANSS showed a statistically significant improvement at the end of the study. Olanzapine plasma levels (PL) ranged from 5 to 120 ng/ml (mean 33.15 ng/ml ± 28.28 S.D.) and showed a positive correlation with OLZ dosage. A significant curvilinear correlation between OLZ PL and clinical improvement (BPRS, PANSS and HRS-D percent of amelioration) was observed.

Conclusion

Olanzapine plasma level determination seems to be a useful tool in optimizing acute treatment particularly for more problematic cases.

Right-Hemisphere Superiority in the Discrimination of Spatial Phase

Visual field differences have been investigated in various detection and discrimination tasks for simple sinusoidal gratings or for complex gratings composed of two sinusoids of spatial frequencies f and 3 f. Sinusoidal gratings were employed to evaluate contrast sensitivity, subthreshold summation effects, aftereffects of adaptation to a high-contrast grating, and spatial-frequency discrimination. The tasks with complex gratings were detection of the 3 f component in the presence of a high-contrast f component and spatial-phase discrimination. The stimuli were presented either in the left or in the right visual hemifield. The results indicate a lack of lateralization for detection and spatial-frequency discrimination of sinusoidal gratings, and for the bandwidth of subthreshold summation effects and adaptation aftereffects, whereas the detection of the 3 f component in the presence of a high-contrast f component, as well as spatial-phase discrimination of f + 3 f gratings, show a left-field advantage. This suggests a right-hemisphere superiority in the processing of spatial phase.

The Dependence of Monocular Rivalry on Spatial Frequency

The effect of change in spatial frequency on the alternation rate of two crossed gratings was measured. The rate was found to decrease with increase in spatial frequency, but to change only little with contrast. Low alternation rate was observed for crossed square-wave gratings compared to crossed sine-wave gratings; here the rate of rivalry is largely dependent upon the presence or absence of the first three harmonic components rather than the higher harmonics which contribute to the sharp edges of the square wave. The results are compared with those for some ambiguous figures.

Epidemiology and outcome of systemic infections due to saprochaete capitata: case report and review of the literature

A case of systemic infection due to Saprochaete capitata in a patient with chronic lymphocytic leukemia is described. A review of the literature was conducted to identify all reported cases of this infection described between 1977 and August 2013. One hundred and four cases (included the present one) were identified. The median age of the patients was 56 years and 56% were males. Comorbidities included acute myeloid leukemia (52%), acute lymphoid leukemia (22%), other hematological malignancies (13%) and non-hematological diseases (9%). At the time of the infection, 82% of the patients were neutropenic. In 75% of the cases, the yeast was isolated from blood culture, in 25% from other sterile sites. Empirical treatment was done in 36% of the cases. Fifty-eight percent of the individual cases were treated with a combination or a sequential antifungal therapy. Amphotericin B was the antifungal drug most commonly used, followed by voriconazole and itraconazole. The overall crude mortality was 60%. Saprochaete capitata causes life-threatening infections in neutropenic patients. This comprehensive literature review may help the clinician to optimize the management of this rare infection.

Clinical outcome and tolerability of duloxetine in the treatment of major depressive disorder: a 12-week study with plasma levels

Duloxetine (DLX) is a dual serotonin and norepinephrine reuptake inhibitor that has been recently approved for the treatment of major depressive disorder (MDD). However, little is known about the relationship between DLX plasma levels and clinical response. The aims of this open-label study were 1) to assess clinical outcome and tolerability of DLX by means of clinician and patient assessments and 2) to evaluate the value of plasma DLX levels as predictors of clinical response and tolerability. This was a naturalistic, open-label study of 45 outpatients affected with MDD (16 men and 29 women), who received DLX at doses of 30-120 mg/day and were evaluated at baseline (T0) and after 2, 4 and 12 weeks (T1-3). The assessments included the Hamilton Rating Scales for Depression (HRSD) and Anxiety (HRSA), Clinical Global Impression-Severity (CGI-S), Beck's Depression Inventory (BDI) and a mood visual analogue scale (VAS). Compared with T0, there were significant improvements in HRSD at T1, T2 and T3 (P < 0.001), in HRSA, CGI-S and the self-administered BDI at T2 and T3 (P < 0.001), and in the VAS scores shown at T3 (P = 0.01). DLX treatment was safe and well tolerated. Plasma DLX levels at T2 ranged from 5 to 135 ng/mL (mean +/- SD = 53.56 +/- 39.45) and correlated almost significantly with the DLX dose (r = 0.35; P = 0.069). There was a significant curvilinear quadratic relationship between the improvement of HRSA scores and plasma DLX levels (R(2) = 0.27; P = 0.02). The incidence of anxiety or irritability was associated with the highest plasma levels. Our findings suggest that monitoring plasma DLX levels may be helpful in predicting better treatment responses and tolerability. The present data seem to suggest an optimal anxiolytic efficacy of DLX at intermediate plasma levels.

Geniculate neural plasticity in kittens after exposure to periodic gratings

Kittens were exposed for 2 hours a day to a periodic vertical grating during the first 10 weeks after birth, and otherwise kept in darkness. The spatial frequency of the grating fell in the range of highest contrast sensitivity of normal cats. After the 10-week exposure period, cortical evoked potentials and lateral geniculate mass responses to alternating gratings showed a reduced amplitude for the spatial frequency of exposure. This reduction was independent of grating orientation. An analysis of orientational sensitivity of cortical units did not show any bias in favor of the vertical orientation.

Red cell blood groups of East African Zebu cattle

A total of 146 East African Zebu, 41 Zebu-Hereford crosses and 24 Ayrshire-Norwegian Red Cattle crosses have been investigated with cattle red cell reagents characterizing blood factors in eleven systems. With a battery of 36 selected reagents the average number of blood factors in Zebu was 20.1 which differs significantly from the average of 12.5 in the Ayrshire crosses. Factor frequencies for the A, C and S systems and gene frequencies for the F, L, M, Z, R' and T' systems are presented. The B system factors in four Zebu bulls could be grouped into eight different phenogroups by utilizing the blood types of dam-offspring pairs.

Ziprasidone outcome and tolerability: a practical clinical trial with plasma drug levels

INTRODUCTION

The aim of this study was to evaluate clinical outcomes and the tolerability of ziprasidone in relation to its plasma levels.

METHODS

Thirteen inpatients affected by schizophrenia were included in the study after an acute exacerbation phase. Ziprasidone monotherapy was administered for a period of eight weeks at a mean dose of 123.07+/-30.38 mg/day. Plasma concentrations were measured by high-performance liquid chromatography.

RESULTS

Nine patients completed the study. A significant clinical improvement was observed, especially in negative symptoms ( P<0.05), and there was a significant improvement in extrapyramidal symptoms ( P<0.01). Clinical laboratory tests, such as ECG and weight, did not significantly change from baseline. Plasma ziprasidone levels ranged from 20 ng/mL to 160 ng/mL (mean: 75.8 ng/mL) and were significantly related to the improvement in negative symptoms.

DISCUSSION

The study showed that ziprasidone was effective and tolerable, that use of ziprasidone was characterized by an absence of extrapyramidal symptoms and weight gain, and that no alterations in clinical laboratory tests occurred. The findings suggest a relationship between plasma levels and the clinical response to negative symptoms of schizophrenia.

Sleep's quality disorders in patients with hypertension and type 2 diabetes mellitus

Sleep is one of the most important factors contributing to health. Although same studies examining the relationship between sleep duration and mortality, has not been fully discussed. We consecutively studied two hundred and fifty Caucasian subjects, normoweight, who were referred for ambulatory blood pressure monitoring (APM). Quality of sleep was evaluated through the Pittsburgh Sleep Quality Index (PSQI). PSQI assessed subjective sleep quality of the past 4 weeks and was administered during the personal interview. A global PSQI > or =5 has a diagnostic sensitivity of 89.6 and specificity of 86.5 in distinguishing "poor sleepers"(PSQI > or =5) from "good sleepers" (PSQI <5) subjects. Hypertension, type 2 diabetes mellitus and sleep's quality disorders were reported respectively in 53.4%, 12.5% and 35.2% of the total population examined. The prevalence of hypertension was 87.1% in "poor sleepers" subjects versus 35.1% in "good sleepers" subjects (p<0.0001). Our results permit to conclude that, as the sleep-disordered breathing, also the sleep's quality disorders, evaluated by PSQI, are associated with significant comorbidities, as hypertension and diabetes mellitus. We hypothesize that the valuation of the quality of sleep through the Pittsburgh Sleep Quality Index (PSQI) could be considered in screening for cardiovascular risk.

Circadian rhythm of autonomic activity in non diabetic offsprings of type 2 diabetic patients

The aim of the present study was to evaluate, by heart rate variability (HRV) with 24-hours ECG Holter (HRV), the circadian autonomic activity in offspring of type 2 diabetic subjects and the relation with insulin-resistance. METHODS: 50 Caucasian offsprings of type 2 diabetic subjects were divided in two groups: insulin-resistant offsprings (IR) and non insulin-resistant offsprings (NIR). Autonomic nervous activity was studied by HRV. Time domain and spectral analysis (low frequency, LF, and high frequency, HF, provide markers of sympathetic and parasympathetic modulation when assessed in normalized units) were evaluated. RESULTS. Time domain showed a reduction of total SDNN in IR (p < 0.001) and NIR (p 0.047) versus controls. Spectral analysis showed a total and night LF higher in IR and NIR than in control group (all p < 0.001). CONCLUSION. In frequency domain, the analysis of sympathetic (LF) and parasympathetic (HF) component evidenced an association between the offspring of type 2 diabetic subjects and a sympathetic overactivity. A global reduction and alteration of circadian rhythm of autonomic activity are present in offspring of type 2 diabetic patients with and without insulin resistance. The data of our study suggested that an autonomic impairment is associated with the familiarity for type 2 diabetes independently to insulin resistance and that an impairment of autonomic system activity could precede the insulin resistance.

Efficacy of clozapine in a non-schizophrenic patient with psychogenic polydipsia and central pontine myelinolysis

Clozapine is an atypical antipsychotic drug that has been demonstrated to be a highly effective treatment for polydipsia in schizophrenic patients. The authors report the first case of a non-schizophrenic patient affected by polydipsia and central pontine myelinolysis who was successfully treated with clozapine.

A cortical area that responds specifically to optic flow, revealed by fMRI

The continuously changing optic flow on the retina provides information about direction of heading and about the three-dimensional structure of the environment. Here we use functional magnetic resonance imaging (fMRI) to demonstrate that an area in human cortex responds selectively to components of optic flow, such as circular and radial motion. This area is within the region commonly referrred to as V5/MT complex, but is distinct from the part of this region that responds to translation. The functional properties of these two areas of the V5/MT complex are also different; the response to optic flow was obtained only with changing flow stimuli, whereas response to translation occurred during exposure to continuous motion.

Lack of cortical contrast gain control in human photosensitive epilepsy

Television and video games may be powerful triggers for visually induced epileptic seizures. To better understand the triggering elements of visual stimuli and cortical mechanisms of hyperexcitability, we examined eleven patients with idiopathic photosensitive epilepsy by recording visually evoked potentials (VEPs) in response to temporally modulated patterns of different contrast. For stimuli of low-medium, but not high, temporal frequency, the contrast dependence of VEP amplitude and latency is remarkably abnormal for luminance contrast (black-white), but not so for chromatic contrast (equiluminant red-green) stimuli. We conclude that cortical mechanisms of contrast gain control for pattern stimuli of relatively low temporal frequency and high luminance contrast are lacking or severely impaired in photosensitive subjects.

Developmental changes in optokinetic mechanisms in the absence of unilateral cortical control

Animal models suggest that the asymmetry of monocular optokinetic nystagmus (OKN) in young infants can be explained by a direct pathway from retina to the midbrain nucleus of the optic tract. However, earlier studies with hemispherectomized infants showed no evidence for OKN responses towards the damaged cortex that could be ascribed to this subcortical pathway. In longitudinal testing of two infants with very extensive unilateral cortical damage, we have now shown that OKN responses in both directions do occur before 10 months of age. OKN towards the damaged cortex, indicating functioning of the direct pathways in the absence of cortical control, drops out in the later development. The neural circuitry responsible for OKN in humans appears to undergo a plastic reorganization.

Irritable bowel syndrome in patients with Blastocystis hominis infection

The prevalence of Blastocystis hominis in stool specimens of individuals with gastrointestinal symptoms was evaluated to study a possible link between the protozoan and the irritable bowel syndrome. According to the Rome diagnostic criteria, 388 patients were evaluated. Altogether, 81 patients were classified as affected by irritable bowel syndrome. Blastocystis hominis was recovered from the stools of 38 subjects, 15 of whom belonged to the group with irritable bowel syndrome (P = 0.006). In addition, patients with irritable bowel syndrome were significantly more likely to have five or more Blastocystis hominis organisms per field (P = 0.031). In conclusion, there was a set of patients with irritable bowel syndrome in whom the presence of Blastocystis hominis may not be incidental.

The effects of ageing on reaction times to motion onset

We have measured reaction time (RT) to motion onset in two groups of subjects (average ages: 70 and 29 years), for horizontal gratings of 1 c deg-1, modulated in either luminance or colour (equiluminant red-green), for various contrasts and speeds. For both old and young subjects, RTs depended on both speed and contrast, being faster at high speeds and high contrasts, and showed a stronger contrast dependency for chromatic gratings. The older subjects were systematically slower than the younger subjects. The difference between old and young RTs varied with condition, being 30-40 ms more at the slow than at the fast speed. The relative difference in RTs in different stimulus conditions shows that at least some of the increase in response time with age has a sensory origin. The results relate well to previous work on visual evoked potentials.

Behavioural visual acuity of wild type and bcl2 transgenic mouse

Since the advent of gene manipulating techniques, it has become increasingly important to study the neural functional properties of the mouse. The bcl2 gene has a powerful inhibitory action on naturally occurring cell death. As a consequence the brain of bcl2 overexpressing mouse is 1.5 times bigger than the brain of a wild type animal and the retina has more than twice the ganglion cells than normal (Martinou, Dubois-Dauphin, Staple, Rodriguez, Frankowski, Missotten, Albertini, Talabot, Catsicas, Pietra, & Huarte (1994). Neuron, 13: 1017-1030). Since in most mammals the upper limit of behavioural visual acuity is imposed by ganglion cells density, the visual acuity should be higher in bcl2 mice than in wild type mice. We measured behavioural visual acuity in wild type and transgenic mice and, contrary to the expectation, we found it to be of the same order (0.5-0.6 c/deg) in the two groups of animals, indicating that an increase in ganglion cells density is not effective in improving visual resolution.

Reaction time to motion onset of luminance and chromatic gratings is determined by perceived speed

We measured reaction times for detecting motion onset for sinusoidal gratings whose contrast was modulated in either luminance or chromaticity, for various drift rates and contrasts. In general, reaction times to chromatic gratings were slower than to luminance gratings of matched cone contrast, but the difference in response depended critically on both contrast and speed. At high image speeds there was virtually no difference, whereas at low speeds, the difference was pronounced, especially at low contrasts. At high image speeds there was little dependence of reaction times on contrast (for either luminance or colour), whereas at low speeds the dependence was greater, particularly for chromatic stimuli. This pattern of results is reminiscent of those found for apparent speed of drifting luminance and chromatic gratings. We verified the effects of contrast on perceived speed, and went on to show that the effects of contrast on reaction times are totally predictable by the perceived speed of the stimuli, as if it were perceived rather than physical speed that determined reaction times. Our results support that idea of separate systems for fast and slow motion (with separate channels for luminance and colour at slower speeds), and further suggest that apparent speed and reaction times may be determined at a similar stage of motion analysis.

Cyclosporiasis in a traveler returning from South America

Cyclospora is a coccidian, previously referred to as a cyanobacterium-like body, with an epidemiology similar to that of Cryptosporidium parvum. In recent years, several studies have shown that Cyclospora is not a rare opportunistic pathogen but rather is the cause of common, worldwide intestinal infections in healthy adults and children. Previous reports of diarrhea resulting from Cyclospora sp. have been linked to travelers and immunocompromised patients. The species has a worldwide distribution. Although Cyclospora infection has been reported from Southeast Asia, Papua New Guinea, Indonesia, India, Pakistan, Nepal, the Middle East, North Africa, the United Kingdom, the Caribbean, the United States, Central America, and South America, the true prevalence of this parasite in any population is unknown. The parasite is associated with prolonged self-limiting and relapsing watery diarrhea, anorexia, fatigue, and sometimes myalgia. Fever is infrequent.

Responses to chromatic and luminance contrast in glaucoma: a psychophysical and electrophysiological study

Increasing anatomical evidence indicates that large retinal ganglion cells (M-cells) are preferentially damaged in primary open angle glaucoma (OAG), while the smaller ganglion cells (P-cells) are relatively spared. In 13 patients with defined OAG and modest visual field defects, we evaluated the responses to stimuli that are expected to involve primarily the function of the P-pathway and compared them with those of control subjects. The psychophysical contrast sensitivity (CS), the PERG and the VEPs were measured for red-green gratings of pure chromatic contrast, as well as yellow-black gratings of pure luminance contrast. As compared with controls, OAG patients had reduced CS for both luminance and chromatic contrast stimuli by about 6 dB. PERGs and VEPs to luminance stimuli were little affected, whereas those to chromatic stimuli were both reduced in amplitude and delayed. These results indicate that visual dysfunction in glaucoma is not selective for the M-pathway, and that responses to equiluminant colour-contrast stimuli may be of diagnostic value.

Visual perceptual learning: a sign of neural plasticity at early stages of visual processing

Examples of perceptual learning in various visual tasks are briefly reviewed. In spite of the variety of the tasks and stimuli, in most of these examples the effects of learning are specific for stimulus parameters and retinal location and transfer interoccularly. Enduring practice effects can be acquired within a single experimental session and/or progressively from one session to the next one, often continuing to improve until thousands of trials have been performed. The consolidation of learning effects from one session to the next one may occur in the waking state as well as during a normal night sleep, but is strongly dependent on the type of sleep. Improvement in performance does not require that the subject is informed of the correctness of his/her responses, but needs attention to the task: learning does not take place for the stimulus attributes that are not attended to. All this suggests that visual perceptual learning involves plastic changes at early neural processing levels, which are dependent for their induction and consolidation on the general behavioural state of the subject, such as attentiveness and type of sleep.

Visual ageing: unspecific decline of the responses to luminance and colour

We have investigated whether ageing affects selectively the responses to equiluminant patterns of pure colour contrast. In two groups of subjects (mean ages 29 and 72 yr) contrast thresholds were measured psychophysically for the detection and for the discrimination of the direction of motion of drifting gratings. The gratings were modulated either in pure luminance contrast (and uniform colour), or pure chromatic contrast (red-green equiluminant gratings). In subjects of the same age groups, visual evoked potentials (VEP) were recorded in response to gratings with either pure luminance contrast or pure colour contrast sinusoidally reversed in contrast at various temporal frequencies. It was shown that psychophysical contrast sensitivity for equiluminant patterns deteriorates significantly with age, and VEP latency increases. However, these effects of ageing on the responses to patterns of pure colour contrast are substantially the same as those observed in the same subjects for stimuli with pure luminance contrast. The results suggest that ageing causes a small and unspecific decline of the response of the visual system to luminance and colour contrast.

Development of the temporal properties of visual evoked potentials to luminance and colour contrast in infants

We have studied the development of the temporal characteristics of the pattern visual evoked potentials (P-VEPs) in response to contrast reversal of patterns of low spatial frequency (0.1 c/deg) of either pure luminance contrast (yellow-black plaid patterns) or pure colour contrast (equiluminant red-green plaid patterns) in 15 infants between 6 and 30 weeks of age. High contrast patterns were modulated temporally either sinusoidally at various temporal frequencies to elicit steady-state responses, or abruptly at a low temporal frequency to elicit transient responses. Analysis of both the transient and steady-state responses suggests the existence of three different mechanisms contributing to the infant and adult P-VEP responses at low, medium and high temporal frequencies. The responses at the three different temporal frequency ranges have different time constants, and develop at different rates. The low frequency response predominates at 8 weeks, where it spans the range 1-6 Hz with an apparent latency of about 230 msec, for both colour and luminance stimulation. This response increases in bandwidth and decreases in latency progressively with age, at a similar rate for luminance and colour contrast, up to 14 weeks. After 14 weeks, the luminance response undergoes major changes, with the emergence of a new response with a shorter latency (about 100 msec) and a peak activity near 10 Hz. This mid-frequency response matures further with age, until it dominates the whole response of the adult P-VEP to luminance contrast. It also makes a contribution to the chromatic response at frequencies above 10 Hz, generating the characteristic double-peaked amplitude response in adults. However, its contribution is very limited below 10 Hz, where the response latency is 140 msec in adults, as it was at 14 weeks of age. A third component is evident at very high temporal frequencies of the luminance response as early as 6 weeks, extending up to 15 Hz in 8-week-olds and up to 25 Hz for older infants. It remains apparent up to 18 weeks, thereafter being swamped by the major mid-frequency response. The apparent latency of response over this frequency range is about 70 msec at all ages. The development of transient P-VEPs paralleled that of the steady-state P-VEPs. At all ages there was an early negative component (N70) at about 70 msec, corresponding to the fast steady-state response at high frequencies for luminance contrast. Before 14 weeks, the luminance and chromatic transient response had the same morphology, with a single major peak of similar latency to the apparent latency of the low temporal frequency response. After this age, the morphology of the luminance response changed, particularly in the first 100 msec, consistent with the emergence of the mid-frequency response. We discuss whether the high-frequency component may represent pre- or early post-synaptic cortical activity, already mature by 8 weeks, and how the different maturation rates of the mid and high-frequency components may reflect different intra-cortical circuitry for colour and luminance.

Nerve growth factor preserves behavioral visual acuity in monocularly deprived kittens

Recent electrophysiological and anatomical experiments in rats and cats have shown that treatment with the neurotrophic factor-nerve growth factor (NGF)-prevents the effects of monocular deprivation (MD) at the level of visual cortex and lateral geniculate nucleus. We tested whether NGF treatment was effective in preventing MD effects on visual behavior of monocularly deprived kittens. Behavioral visual acuity was measured in kittens that had been monocularly deprived and treated intraventricularly with NGF for 2 weeks during the critical postnatal period. The detrimental effects of MD on behavioral visual acuity were found to be largely prevented by NGF treatment.

Pattern-reversal electroretinogram in response to chromatic stimuli: I. Humans

We have studied the steady-state PERG in human subjects in response to red-green plaid patterns modulated either in luminance or in chromaticity or both. By varying the relative luminance of the red and green components, a value could be obtained at which the PERG amplitude was either minimum or locally maximum. This always occurred at equiluminance, as measured by standard psychophysical techniques. PERG amplitude and phase were measured as a function of spatial and temporal frequency of sinusoidal contrast reversal. In both space and time, the response to chromatic patterns was low-pass, while that to luminance was band-pass, and extended to higher spatial and temporal frequencies. The phase of the PERG to chromatic stimuli was systematically lagged compared with that to luminance stimuli, by an amount corresponding to about 20 ms under our experimental conditions. The variation of phase with temporal frequency suggested an apparent latency of about 67 ms for color contrast compared with 47 ms for luminance. These estimates were confirmed with separate measurements of transient PERGs to abrupt contrast reversal. For both luminance and chromatic stimuli, the amplitude of PERGs increases with increasing stimulus contrast. By summing vectorially the responses to appropriate luminance and chromatic contrasts, we were able to predict with accuracy the response as a function of color ratio (ratio of red to total luminance). The above findings all agree with those reported in the accompanying paper for the monkey PERG (Morrone et al., 1994), and indicate that the differences in response latency and integration time of luminance and chromatic stimuli observed by psychophysical and VEP techniques may arise at least in part from the properties of retinal mechanisms.

Pattern-reversal electroretinogram in response to chromatic stimuli: II. Monkey

We have recorded steady-state PERGs from five macaque monkeys in response to red-green plaid patterns reversed sinusoidally in contrast. The patterns had either a pure luminance contrast (red-black, green-black, yellow-black), pure red-green color contrast, or a variable amount of luminance and color contrast. By varying the relative luminance of the red-to-total luminance (color ratio) of red-green patterns, a value could be obtained at which the PERG amplitude was either minimum or locally maximum, and the phase was most lagged. This value was very similar to that producing equiluminance in human observers, and was considered to be equiluminance for the monkey. The phase of the PERG to chromatic stimulus was systematically lagged compared with that of luminance stimuli, by an amount corresponding to about 10-20 ms under our experimental conditions. The variation of phase with temporal frequency suggested an apparent latency of about 80 ms for color contrast compared with 63 ms for luminance. These estimates were confirmed with separate measurements of transient PERGs to abrupt contrast reversal. As a function of temporal frequency, the chromatic PERG function was clearly low-pass with a cutoff around 15 Hz, whereas that to luminance was double-peaked and extended to higher temporal frequencies, around 30 Hz. For both luminance and chromatic stimuli, the amplitude of PERGs increases with increasing stimulus contrast. By summing vectorially the luminance and chromatic responses of appropriate contrasts, we were able to predict with accuracy the response as a function of color ratio. In two monkeys, the optic chiasm was sectioned sagittally causing total degeneration of ganglion cells in the nasal retina, without affecting the temporal retina (verified by histology). In these animals, there was a strong response to both luminance and chromatic patterns in the temporal retinae, but none to either type of pattern in the nasal retinae, suggesting that the PERG to both luminance and chromatic stimuli arises from the inner-retinal layers. Electrophysiological studies suggest that the PERG to chromatic stimuli is probably associated with the activity of P-cells. P-cells may also make a major contribution to the PERG of luminance stimuli, although M-cells may also participate. The above findings on normal monkeys all agree with those reported in the accompanying paper for humans (Morrone et al., 1994), so similar conclusions can probably be extended to human PERG.

The pattern electroretinogram in response to colour contrast in man and monkey

Steady-state pattern-reversal electroretinograms (PERG) were recorded from both monkeys and humans in response to tartan patterns modulated in both space and time in either luminance contrast or chromatic contrast. In both species, all types of patterns cause a strong modulation of the second-harmonic of the PERG. There was no measurable dependency of the PERG on the colour of the stimulus per se: both in humans and monkeys, stimuli with green-black, red-black or yellow-black modulation of the same mean luminance and of the same contrast, produced identical results. However, chromatic stimuli with modulation between equiluminant red and green produced a qualitatively different PERG: the amplitude was lower, particularly at high temporal frequencies, and there was a clear phase lag corresponding to a difference in processing time of about 20 ms.

Development of infant contrast sensitivity to chromatic stimuli

We have monitored the development of contrast sensitivity to equiluminant red-green chromatic patterns by monitoring visual evoked potentials (VEPs) in 13 infants. The results confirm our previous report [Morrone, Burr and Fiorentini, Proceedings of the Royal Society B, 242 (1990a)] that, before 7-8 weeks of age, there was no response to purely chromatic stimuli, while at the same age luminance stimuli of 20% contrast produced reliable responses. At all ages (even before the onset of a chromatic response) the colour mixture to yield equiluminance was similar to that of adults, suggesting that the relative proportion and efficacy of medium- and long-wave cones is similar for infants as for adults. For both luminance and chromatic stimuli, amplitude increased roughly linearly with log-contrast, so sensitivity thresholds could be predicted by linear extrapolation to the abscissa. Detailed contrast sensitivity curves were measured for four infants at various ages. The results show that luminance and chromatic contrast sensitivity develop independently at different rates, probably reflecting differential development of postreceptoral neural mechanisms.

Eye alignment and cortical binocularity in strabismic kittens: a comparison between tenotomy and recession

Interocular alignment was assessed by corneal light reflex photography in 15 normal and 26 strabismic kittens. Strabismus was induced at 3-4 weeks of age by severing one extraocular muscle (tenotomy), by cutting and reinserting the muscle at another position on the ocular globe (recession), or by combining recession of the medial rectus muscle with resection of the lateral rectus muscle of the same eye. Nineteen strabismic and five normal kittens were followed longitudinally from 12 days to about 6 months of age. Three out of six longitudinally followed tenotomized cats and six out of the 13 recessed cats conserved their postoperative ocular deviation throughout the testing period ("large-angle strabismics"). Three tenotomized and seven recessed cats showed a transient deviation for 1-2 weeks after surgery, after which the interocular deviation diminished to values found in normal cats ("microstrabismic" cats). Both recessed-resected cats showed a transient interocular deviation. In spite of their different developmental histories, all cats showed a clear breakdown of binocularity in area 17. Large-angle strabismics showed a dominance of the non-operated eye, while in microstrabismic cats, both eyes were equally effective in driving cortical cells. It thus appears that a transient strabismus is sufficient to produce a reduction of binocularity in area 17.

Potential hazards of tracheobronchial suctioning

Tracheobronchial suctioning is a routine practice frequently carried out in intensive care units (ICUs). It is required when the normal coughing mechanism is inadequate or disrupted; for example, where there is underlying respiratory or neurological disease, or where the cough is deliberately suppressed by sedative, muscle relaxants or anaesthetic agents while a patient is undergoing intermittent positive pressure ventilation. The procedure is carried out via a nasotracheal, orotracheal or tracheostomy tube. During the performance of this intervention, the skilled nurse is aware of the risks to which the patient is exposed and endeavours to prevent or minimise possible complications. In the following account of complications that may occur during or as a result of the procedure these have been classified as immediate, intermediate and later complications, as shown in Table 2. The purpose is to stimulate greater awareness of the hazards involved in this common everyday practice in intensive care units.

Development of temporal properties of pattern electroretinogram and visual evoked potentials in infants

The postnatal development of the temporal properties of the responses to pattern contrast reversal has been studied by recording simultaneously the pattern electroretinogram (PERG) and visual evoked potentials (PVEP) in infants 3-22 weeks old. The stimulus grating (0.5 c/deg) was either reversed in contrast sinusoidally at frequencies 4-10.5 Hz to study the temporal frequency function of steady-state responses, or square-wave reversed at 1 Hz to evaluate the peak latency of transient responses. Developmental changes of the shape and bandwidth of the temporal frequency function of both PERG and PVEP occur post-natally and are particularly pronounced between 13 and 20 weeks from birth, possibly indicating deferred maturation of classes of retinal and central neurons with higher temporal resolution. The peak latency of the PERG decreases during the age period tested to approach adult values towards the end of the fifth month. The rate of decrease of the peak latency of the PERG differs from that of the PVEP, indicating that post-retinal factors contribute largely to the maturation of the latter, especially in the earliest life period.

The effects of aging on the pattern electroretinogram and visual evoked potential in humans

We have recorded patterns electroretinograms (PERGs) and visual evoked potentials (VEPs) from 14 elderly subjects (mean age 72 yr) and 12 young subjects (mean age 21 yr) in response to stimulation by high contrast sinusoidal grating patterns of variable spatial frequency (at 9 Hz) and temporal frequency (at 1.7 c/deg). The major effect of aging on the PERG was an aspecific reduction in amplitude (of about 40%) at most spatial and temporal frequencies, together with a small but systematic phase lag. Control measurements suggest that senile miosis may be responsible for the phase lag, but not for the reduction in amplitude. The effects of aging on the VEP were more dramatic and depended on the spatial and temporal properties of the stimulus. VEP amplitudes (at 1.7 c/deg) were significantly lower for the aged at low temporal frequencies (below about 6 Hz), but were similar at high temporal frequencies. At 9 Hz, there was no effect of spatial frequency on VEP amplitude. At high temporal frequencies (above 10 Hz), the latencies of VEPs (estimated from the rate at which phase varied with temporal frequency) were similar for old and young (94 and 99 msec respectively). Below 10 Hz, however, the latencies of the old observers was much greater (153 compared with 108 msec). The second-harmonic phase of VEPs of the old but not the young decreased considerably with spatial frequency, by about 1.9 pi radians (52 msec) over the range from 0.5 to 11 c/deg. The selective reduction in amplitude at low temporal frequencies, the longer latencies at low temporal frequencies and the phase lag at high spatial frequencies are consistent with the hypothesis that mechanisms sensitive to high spatial and low temporal frequencies are selectively degraded by aging.

Electro-physiological investigation of edge-selective mechanisms of human vision

This study investigates the spatial and temporal characteristics of human visual mechanisms that respond selectively to the polarity of edges. The technique was to record steady-state visual evoked-potentials (VEPs) while visually stimulating with a sawtooth waveform (a series of edges of the same polarity) periodically reversing in contrast (and hence edge-polarity) at a suitable frequency. To ensure that phase-locked VEPs resulted from polarity reversal (rather than local luminance modulation) the stimuli were randomly jittered to a new position between each contrast reversal. The jittered stimulus elicited strong and reliable second-harmonic modulation, usually about one-fifth the amplitude of standard VEPs under similar conditions. The amplitude and extrapolated thresholds of polarity-specific VEPs (relative to standard VEPs) did not vary with eccentricity (up to 10 degrees) or with stimulus orientation. The dependency on spatial frequency was similar to that of standard VEPs, but the polarity-specific VEPs tended to peak at lower temporal frequencies. Perhaps the clearest difference in the two types of VEPs was in the estimated response latency, about 140 msec for the polarity VEPs, compared with 90 msec for standard VEPs.

Epidemiological surveillance of staphylococcal resistance

The aim of our investigation was to characterize better the possible changes in staphylococcal susceptibility to some antimicrobial agents. We considered the staphylococcal strains isolated between June 1986 and June 1989 and held responsible for proved bacterial infections. In this relatively short time we observed a moderate increase in methicillin resistance. Compared with methicillin-sensitive strains, methicillin-resistant isolates showed minor susceptibility to most antimicrobial agents; nevertheless, vancomycin, teicoplanin, cefamandole, imipenem, fluoroquinolones and netilmicin, according to our results, appear at present the most reliable antistaphylococcal antibiotics.

Visual field asymmetries in pattern discrimination: a sign of asymmetry in cortical visual field representation?

A visual field asymmetry is described relative to the discrimination of mirror symmetric bars with ramp-like luminance profiles. Along the vertical meridian the discrimination is better performed for patterns oriented parallel to the meridian than for patterns oriented orthogonally at all eccentricities tested (2-8 deg). Along the horizontal meridian, the preference for radially oriented stimuli is present at 2 deg from the fovea, but vanishes at larger eccentricities. The meridional asymmetry thus revealed psychophysically may reflect asymmetries in the representation of the vertical and horizontal meridians in the human visual cortex.

Development of contrast sensitivity and acuity of the infant colour system

We have monitored the development of infant colour vision by measuring chromatic contrast sensitivity and acuity in eight young infants over a period of 6 months. Steady-state visual evoked potentials (VEPS) were recorded in response to both chromatic (red-green) and luminance (red-black or green-black) patterns that were reversed in contrast over time. For most infants, no response could be obtained to chromatic stimuli of any size or contrast before 5 weeks of age, although luminance stimuli of 20% contrast gave reliable responses at that age. When responses to chromatic stimuli first appeared, they could be obtained only with stimuli of very low spatial frequency, 20 times lower than the acuity for luminance stimuli. Both contrast sensitivity and acuity for chromatic stimuli increased steadily, more rapidly than for luminance stimuli. As the spectral selectivities of infant cones are similar to those of adults, the difference in rate of development of luminance and chromatic contrast sensitivity and acuity stimuli probably reflects neural development of the infant colour system.

Acute meningococcaemia: a case study

A 20-year-old female presented with sudden onset of abdominal pain, diarrhoea and vomiting progressing to fever, tachycardia and mild hypotension. Within 12 hours, a petechial rash appeared on the face and abdomen, spreading to the extremities. Laboratory findings confirmed the diagnosis of acute meningococcaemia. Clinical features of endotoxic shock, vasculitis and skin necrosis rapidly ensued. Aggressive treatment to control the septicaemia, disseminated intravascular coagulation and unstable cardiovascular state ultimately proved successful. Approximately 6 weeks later, amputation of some of the digits and extensive skin grafting were carried out in the Regional Burns Unit. However, serious psychological side effects gradually began to appear which required urgent psychiatric intervention. For an active young woman the challenge of coping with such a severe illness and coming to terms with the disability and disfigurement resulting from it was almost overwhelming. It was, perhaps, particularly hard because of the threat posed to her ambition to complete her nursing education and become a nurse. Little was found in the nursing literature on acute meningococcaemia. But this illness provides considerable challenges not only to those who suffer from it, but also to those who nurse them. A final brief review of published literature on acute meningococcaemia and the clinical manifestations and outcome of it is provided for those who wish to know more about it.

The visual acuity of the lynx

Visual evoked potentials were recorded from the occipital scalp of two anaesthetized Lynx (Lynx europea) in response to alternating gratings of various spatial frequencies and contrasts. The visual acuity of the Lynx was found to be around 5-6 c/deg, i.e. very close to the visual acuity of the cat and by far inferior to human acuity.

Monocular deprivation in split-chiasm kittens does not impair the development of visuo-motor behaviour

Development of visual acuity is known to be impaired by early monocular deprivation. This may be due to lack of visual experience or to abnormal binocular competition. We report here the results of behavioural experiments on monocularly deprived kittens in which the optic chiasm had been split. In these kittens it has been found that visual acuity of the deprived eye is as good as the visual acuity of the non-deprived eye, namely 2-2.5 c/deg.