Selection of Apis mellifera workers by the parasitic mite Varroa destructor using host cuticular hydrocarbons.

The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8-heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound.

Analysis of EEG tracings in frequency and time domain in hepatic encephalopathy.

Spectral EEG analysis in hepatic encephalopathy (HE) is usually performed disregarding the effect of epoch length, statistical errors and equipment noise. A study on these items was carried out. In addition, spectral analysis and a new analysis, performed in time domain, were compared in the assessment of HE. The EEG tracings of 73 cirrhotic patients with HE were analyzed. Artifact-free periods of about 1 min were selected. Equipment noise was measured by short-circuiting all the electrodes. The equipment noise was notable below 1.5 Hz; the best epoch length was 4s and the statistical errors were minimal for the band with the highest relative power. Nineteen per cent of the tracings were unstable. The spectral values were found to be related to liver function and to the degree of HE, whereas the relationship with psychometric variables was poor. The indexes computed by time-domain analysis were found to be better related to psychometric findings. We have provided information on the optimisation of spectral EEG analysis and presented a time-domain analysis giving results related to psychometric tests and liver function.

P300 latency for the diagnosis of minimal hepatic encephalopathy: evidence that spectral EEG analysis and psychometric tests are enough.

BACKGROUND: No gold standard exists to detect minimal hepatic encephalopathy. Event-related evoked potentials (P300 latency) were proposed as the best tool to assess this condition. EEG spectral analysis and psychometric evaluation are also used to assess minimal hepatic encephalopathy. AIMS: The present study aims at comparing these three techniques. PATIENTS: Eighty-six cirrhotic patients without overt hepatic encephalopathy were studied. METHODS: Patients underwent EEG spectral analysis, psychometric evaluation and P300. P300 latency was age-adjusted; psychometric tests were age- and education-adjusted. Values >2Z were considered to be altered. The alteration of at least two psychometric tests was considered for cognitive impairment. RESULTS: At least one of the three indexes was altered in 61% (CI95% = 49-71) patients; EEG spectral analysis was altered in 41% (CI95% = 30-52%) patients, psychometric performance in 34% (CI95% = 24-45%) and P300 latency in 13% (CI95% = 7-22%). P300 latency was altered only in the patients having EEG spectral analysis or psychometric alterations, but for two cases. Psychometric performance and EEG spectral analysis, but not P300 latency, were correlated with indexes of liver function. CONCLUSIONS: P300 latency provided little additional information and was less related to liver function than EEG spectral analysis and psychometrical investigation.

Neuropsychological and neurophysiological evaluation in cirrhotic patients with minimal hepatic encephalopathy undergoing liver transplantation.

BACKGROUND: Cirrhotic patients without overt hepatic encephalopathy may have cerebral function alterations called minimal hepatic encephalopathy (MHE). Our goal was to evaluate the role of partial pressure of ammonia (pNH3), neuropsychological, and neurophysiological assessment in detecting cognitive changes in cirrhotic patients awaiting liver transplantation. MATERIALS AND METHODS: Fourteen cirrhotic patients listed for liver transplant were studied. All patients underwent the neuropsychological battery called PSE. Neurophysiological assessment including spectral EEG (sEEG), evoked potential P300 and pNH3 and venous and arterial ammonia levels was performed in all patients. Four patients were transplanted. RESULTS: Liver disease etiology was alcoholic in four patients, viral in six mixed in two, and cryptogenic in two. PSE scores revealed MHE in 8 patients; sEEG was altered in 6, and P300 in 1. No correlations were detected between P300, sEEG, and PSE. pNH3 and arterial ammonia levels were significantly higher in the subgroup of patients with altered sEEG and were correlated with theta band increase in sEEG but not with pathological PSE scores or P300 wave abnormalities. CONCLUSIONS: The combination of sEEG and PSE, and possibly also pNH3 and arterial ammonia, is useful in detecting cerebral function alterations in cirrhotic patients with no apparent encephalopathy, whereas P300 is not. The diagnosis of MHE obtained using the multimodal approach adopted in this study may enable the adequate treatment of these patients prior to surgery, which includes advising them not to drive and adjusting their priority on the waiting list for OLTx in the light of a condition that cannot be evaluated by Child Pugh score and MELD score.

Neuropsychological-neurophysiological alterations and brain atrophy in cirrhotic patients.

Psychometric performance has been reported to be related to brain atrophy in cirrhotics, but the relationship between brain atrophy and EEG findings is still unknown. The aim of this study was to ascertain the relationship among brain atrophy, EEG, and cognitive performance in cirrhotics. Sixty-eight cirrhotics (age = 55 +/- 10 years; males-66%) underwent psychometric evaluation (Symbol Digit Test, Trail Making Test-Part A, Scan test), EEG recording and spectral analysis (S-EEG), and brain CT scan. Central brain atrophy was ascertained by the following indexes of brain atrophy: the Evans' index, the bicaudate index, the cella media index, the bifrontal index, and the ventricular index; cortical brain atrophy by the sulci index. The severity of liver failure was assessed by the Child-Pugh score: 18% of patients were Child-Pugh Class A, 50% Class B, and 32% Class C. Central and cortical atrophies were found to be correlated with age, but not with the Child-Pugh score. Psychometric performance and the EEG mean dominant frequency (MDF) were found to be correlated with brain atrophy. Multivariate analysis showed that a poor psychometric performance was independently predicted by EEG slowing (MDF: p < 0.01) and by central brain atrophy (cella media index: p < 0.01). In conclusion, brain atrophy was associated with a poor psychometric performance and EEG alterations in cirrhosis. Both brain atrophy and EEG alterations independently predicted cognitive dysfunction in cirrhotic patients.

Vegetarian diets in hepatic encephalopathy: facts or fantasies?

Diet treatment characterized by a reduction in or a selection of food proteins is currently suggested in hepatic encephalopathy. This article is a review of the present knowledge about the characteristics and the rationale of vegetarian diets in cirrhotic patients with overt or latent encephalopathy. In addition, evidence relating diet and encephalopathy and the nutritional features and needs of cirrhotic patients is reported. Finally, the rationale of a diet based on vegetable and milk-derived proteins that may overcome the limits and the possible adverse effects of a strict vegetarian diet is presented.

Prevalence and prognostic value of quantified electroencephalogram (EEG) alterations in cirrhotic patients.

BACKGROUND/AIMS: The electroencephalogram (EEG) is frequently altered in cirrhotic patients. We, therefore, performed a study to ascertain the features and the prognosis of cirrhotic patients without current overt hepatic encephalopathy (OHE) who have EEG alterations. METHODS: A series of 296 consecutive cirrhotic patients who had undergone quantified-EEG was studied. The median follow-up was 442 days, 128 patients had bouts of OHE and 78 patients died from liver-related causes. Another group of 124 cirrhotic patients with a median follow-up of 223 days was examined to validate the prognostic model. RESULTS: EEG alterations were detected in 38% of the patients. The prevalence of EEG alterations was associated with the severity of cirrhosis (class B: odds ratio (OR) = 2.3, 95% confidence interval (CI) = 1.2-4.7; class C: OR = 3.5, 95% CI = 1.6-7.7), but not with the aetiology (alcoholic vs. non-alcoholic: OR = 0.9; 95% CI = 0.5-1.5). The EEG predicted the occurrence of OHE (chi2 = 26; P < 0.001) and mortality (chi2 = 34; P < 0.001), also adjusting for Child-Pugh class by a multivariate analysis. In the patients with a Child-Pugh score of > or = 8, the EEG discriminated between those patients with a higher 1-year risk of OHE (hazard ratio (HR) = 3.3, 95% CI = 1.8-6.1) and death (HR = 3.1, 95% CI = 1.7-5.6). CONCLUSIONS: In conclusion, quantified-EEG had a prognostic value for the occurrence of bouts of OHE and mortality in cirrhotic patients.

Spectral versus visual EEG analysis in mild hepatic encephalopathy.

OBJECTIVE: Spectral EEG analysis has been claimed to reduce subjective variability in EEG assessment of hepatic encephalopathy and to allow the detection of mild encephalopathy. METHOD: To test such assumptions, 43 digital EEG were recorded in 32 cirrhotics without overt encephalopathy or with grade 1 overt encephalopathy; 7 patients were re-tested (2-5 times) in their follow up. All patients underwent psychometric assessment. Nineteen controls were considered. EEG were blindly evaluated by two electroencephalographers and by spectral EEG analysis performed according to 3 different techniques. RESULTS: The reliability of the classification based on spectral analysis (biparietal technique) was higher than that based on a three-degree qualitative visual reading (concordance/discordance = 58/4 versus 46/16 P < 0.01) and comparable with that of semiquantitative visual assessment based on posterior basic rhythm (concordance/discordance = 55/7 P = 0.5). The accuracy of spectral EEG analysis was higher than that of qualitative visual EEG readings alone (90 versus 75%) and comparable to semi-quantitative visual assessment (87%), however, statistical significance was not reached. In the follow-up, the variations of theta and delta relative power were found to be significantly correlated with psychometric variations. CONCLUSIONS: In conclusion, spectral EEG analysis may improve the assessment of mild hepatic encephalopathy by decreasing inter-operator variability and providing reliable parameters correlated with mental status.

Clinical features and survivial of cirrhotic patients with subclinical cognitive alterations detected by the number connection test and computerized psychometric tests.

The prevalence and the clinical implications of subclinical cognitive alterations in cirrhotic patients have not been well defined as yet. Therefore, we performed a study to assess the clinical features and the survival of cirrhotic patients with cognitive alterations detected by the number connection test (NCT) and a set of computerized psychometric tests (Scan, Choice1, and Choice2) measuring the reaction times and the percentage of errors in performing specific tasks. Ninety-four cirrhotic patients (aged 58 +/- 9 years) without overt hepatic encephalopathy and 80 controls (aged 53 +/- 15 years) were consecutively enrolled. The median follow-up in cirrhotic patients was 426 days (lower quartile = 213 days; upper quartile = 718 days). Results of the NCT, Scan test, and Choice2 test were significantly worse in cirrhotic patients, whereas Choice1 did not differ significantly from the controls. In cirrhotic patients, the prevalence of altered psychometric tests was 21% (CI95% = 14%-31%) by NCT, 23% (CI95% =15%-33%) by Scan test, and 20% (CI95% =16%-30%) by Choice2 test. The alterations of NCT, Scan, and Choice2 were found to be related to the severity of liver disease, independently of its etiology. Increased risk of death was found to be associated with altered Scan test (hazard ratio = 2.4; CI95% =1. 1-5.3), or altered Choice2 test (hazard ratio = 2.8; CI95% = 1.2-6. 3). Multivariate regression showed that Scan and Choice2 tests had prognostic value on survival, in addition to Child-Pugh classes in the first year of follow-up.

Study on the Sternberg paradigm in cirrhotic patients without overt hepatic encephalopathy.

Memory dysfunction is reported in cirrhotics. The aim of this paper was to increase insight into memory function of cirrhotic patients without overt hepatic encephalopathy. Eighty-six consecutive cirrhotics without overt hepatic encephalopathy (aged 54+/-10 yr., mean+/-s.d.) and 28 controls (52+/-10 yr.) with comparable education level were enrolled. Seventeen patients were class A, 55 class B, 14 class C according to Child-Pugh classification; 29 had alcoholic cirrhosis. The presence of subclinical signs of central nervous system dysfunction were assessed by Number Connection Test (NCT) and quantified EEG analysis. Memory scanning was evaluated by reaction times (RTs) in the Sternberg paradigm. MANOVA analysis showed that RTs were higher (F1,99=11, p<0.01) and time outs (TOs) more frequent (F1,110=10, p<0.01) in cirrhotics than in controls, whereas button press errors (BPEs) did not differ significantly (F1,110=2, p=n.s.). In cirrhotics, an interaction Child-Pugh class x memory set size was found (F2,146=4, p<0.05), showing exceedingly delayed RTs with greater memory set size in class C patients. Patients with altered NCT had significantly prolonged RTs (F1,71=4, p<0.05) and more TOs (F1,82=11, p<0.01) than patients with normal NCT. Cirrhotics with altered EEG had significantly prolonged RTs (F2,70=6, p<0.01). RTs were found to be correlated to alpha relative power (r=-0.4, p<0.01) and theta relative power (r=0.4, p<0.01). In conclusion, cirrhotics without over encephalopathy, but with NCT or EEG alterations, perform a computerized digit recognition task more slowly and with higher TOs than cirrhotic patients with normal NCT or EEG. In severe liver insufficiency (class C cirrhotics) also an impairment of memory scanning was detected. Sternberg test performance correlates with NCT and quantitative EEG parameters.

Visual attention in cirrhotic patients: a study on covert visual attention orienting.

Attentional dysfunction, which influences overall cognitive productivity, is not well characterized in cirrhotic patients. The aim of this study was to clarify the features of covert visual attention orienting in cirrhotics without overt hepatic encephalopathy. One hundred consecutive cirrhotic patients and 40 controls were enrolled. Visual covert attention orienting was assessed by the Posner test, which evaluates the effect of a cue on visual reaction times. Patients were characterized by the number connection test (NCT) and electroencephalographic (EEG) spectral analysis. The severity of liver disease was graded using standard laboratory parameters and the Child-Pugh's classification. Fifty-five psychometric and EEG evaluations were performed in the follow-up of 17 patients to assess the relationship between the variations of psychometric and neurophysiological findings. NCT and quantified-EEG parameters (altered in 19% and 40% of cirrhotic patients, respectively) were linked to each other and to the severity of liver disease. The Posner test showed a delay of visual reaction times in class B-C cirrhotic patients. Reaction times were correlated with ammonia and EEG parameters. The effect of the cue was higher in cirrhotic patients than in controls, particularly in the invalid position. This study suggests that cirrhotic patients have a reduced activity rate and reduced capacity to disengage attention previously focused on a cue. Such alterations are linked to NCT and EEG findings.

The effect of flumazenil on subclinical psychometric or neurophysiological alterations in cirrhotic patients: a double-blind placebo-controlled study.

It is not yet clear if benzodiazepine receptor ligands, implicated in the pathophysiology of hepatic coma, also have a role in subclinical cognitive or neurophysiological alterations in cirrhotic patients. Therefore, we carried out a double-blind, placebo-controlled study to evaluate the effectiveness of flumazenil, a benzodiazepine antagonist, on brainstem auditory evoked responses and on the number connection test in cirrhotic patients with subclinical neurophysiological or cognitive alterations. Thirteen cirrhotic subjects with subclinical neurophysiological or cognitive alterations were studied. A total of 3 mg of flumazenil or saline was infused intravenously. Before and after the infusion, the number connection test was administered and brainstem auditory evoked responses recorded. After 72 h, patients were crossed over. Flumazenil did not influence brainstem auditory evoked responses or the number connection test. A screening test for benzodiazepines was negative in all subjects. We conclude that benzodiazepine receptor ligands have a negligible role, if any, in the pathophysiology of subclinical neurophysiological or cognitive alterations of cirrhotic patients.

Diagnostic tools for the detection of subclinical hepatic encephalopathy: comparison of standard and computerized psychometric tests with spectral-EEG.

UNLABELLED: The prevalence of subclinical hepatic encephalopathy (SHE) varies according to the diagnostic tool used in its detection. Since a standardised approach to the diagnosis of SHE is not yet available, we compared psychometric tests and EEG spectral analysis. On the same day 32 cirrhotic patients without overt hepatic encephalopathy and 18 controls were assessed by psychometric tests, both standard and computerized (CPT), and by EEG spectral analysis (EEG-SA). The CPT, measuring reaction time (Rt) and errors (er), were Font, Choice1, Choice2 and Scan test. The standard psychometric tests were the number connection test (NCT), the Reitan-B test, the Line Tracing Test [for time: LTT(t) and for errors: LTT(er)], and the Symbol Digit test (SD). Both psychometric tests [Reitan-B test, LTT(er) and CPT but Font (Rt) and Choice2 (er)] and EEG-SA parameters [mean dominant frequency (MDF) and theta power (theta %)] significantly correlated (p < 0.05) with albumin plasma levels. LTT(er), Scan, Font, Choice1 and Choice2 were significantly related to theta % and MDF. There was no control with positive EEG-SA, though one control was positive with LTT(t) and with the number of errors made during Font and Scan tests. The percentage of cirrhotics with positive EEG-SA was 34% (CI95% = 19-53), while 9-66% were positive with psychometric tests, depending on the test considered. In spite of the correlation between neuropsychological and neurophysiological parameters, the diagnostic agreement between EEG-SA and each psychometric test was not high. IN CONCLUSION: 1) neurophysiological and neuropsychological impairment in cirrhotics without overt hepatic encephalopathy were found linked to each other and to hepatic dysfunction; 2) psychometric tests were not sufficiently good predictors of EEG alterations; therefore, neuropsychological tools can not substitute neurophysiological ones to detect CNS dysfunction in liver disease.

Visual attention orienting in liver cirrhosis without overt hepatic encephalopathy.

The attention system in patients with liver cirrhosis has not yet been fully investigated. We therefore studied visual attention orienting in cirrhotic patients without overt hepatic encephalopathy. Seventy cirrhotic patients without overt hepatic encephalopathy (aged 57 +/- 10 yr., mean +/- s.d.) and 55 controls (aged 49 +/- 12 yr.) were enrolled. Visual attention orienting was evaluated by a computerized neuropsychological test. The Reitan A test, commonly used to detect subclinical hepatic encephalopathy, was used to evaluate mental performance. Psychometric test scores were reduced in cirrhotics compared to controls (attention test: neutral condition = 495 +/- 149 vs. 401 +/- 98 msec; valid condition = 434 +/- 110 vs. 398 +/- 84 msec; invalid condition = 485 +/- 146 vs. 392 +/- 110 msec; p < 0.001; Reitan A test = 52 +/- 20 vs. 35 +/- 11 sec., p < 0.001). The attention effect of the cue was found both in controls and cirrhotics; however, it was significantly higher in cirrhotics than in controls (61 +/- 111 vs. 33 +/- 41 msec; p < 0.002). The attention effect was directly correlated with Reitan A test (r = 0.23, p = 0.05) in cirrhotics. In conclusion, in cirrhotic patients without overt hepatic encephalopathy, visual attention orienting was present and focusing to an indexed location had a higher effect on reaction time compared to controls, possibly because of reduced basal arousal.