Excitability in free muscle transfers: an optimal method of monitoring tissue circulation?

Recent methods of postoperative monitoring of free muscle transfers were used in 4 patients operated on with free revascularized gracilis muscle. The contractility/electromyographic (EMG) activity in response to electrical stimulation was used as an index of viability, i.e., intact circulation. However, during operations it was observed that contractions as well as EMG potentials could be evoked 1 to 2 hours after blood flow had been arrested. Muscle excitability was further studied in the gracilis muscle from a patient who had undergone hemipelvectomy; it was found that contractility and EMG potentials were evoked at least 4 hours after circulatory arrest. It thus seems that loss of muscle excitability is not as early a sign of impaired blood supply as recently has been suggested. Spontaneous EMG activity, which can be recorded 2 to 3 weeks after denervation, is reported to be affected earlier than muscle excitability by circulatory arrest. Thus, the recording of spontaneous EMG activity in previously denervated muscles is proposed as an alternative and simple electrophysiological method for post-operative monitoring of vascularization in free muscle transfers.     

Altered neuropeptide Y Y1 responses in mesenteric arteries in rats with congestive heart failure

The aim of the present study was to elucidate if the potentiating effect of neuropeptide Y on various vasoactive agents in vitro is (1) altered in mesenteric arteries from rats with congestive heart failure and (2) mediated by the neuropeptide Y Y₁ receptor. The direct vascular effects of neuropeptide Y and its modulating effects on the contractions induced by endothelin-1-, noradrenaline-, 5-hydroxytryptamine (5-HT)-, U46619-(9, 11-dideoxy-11, 9-epoxymethano-prostaglandin F₂) and ATP, and acetylcholine-induced dilatations were studied in the presence and absence of the neuropeptide Y Y₁ antagonist, BIBP3226 (BIBP3226{(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]- -arginine-amide}). Neuropeptide Y, per se, had no vasoactive effect in the arteries. The potency of endothelin-1 was significantly decreased in congestive heart failure rats. Neuropeptide Y and neuropeptide Y-(13–36) potentiated the endothelin-1-induced contraction in congestive heart failure mesenteric arteries. In 20% of the congestive heart failure rats, sarafotoxin 6c induced a contraction of 31±4%. Neuropeptide Y also potentiated U46619- and noradrenaline-induced contractions but not 5-HT-induced contractions in congestive heart failure arteries. In sham-operated animals neuropeptide Y potentiated noradrenaline- and 5-HT-induced contractions. These potentiations were inhibited by BIBP3226. Acetylcholine induced an equipotent relaxation in both groups which was unaffected by neuropeptide Y. In conclusion, neuropeptide Y responses are altered in congestive heart failure rats. The potentiating effect differs between vasoactive substances. Neuropeptide Y Y₁ and non-neuropeptide Y₁ receptors are involved.     

Cysteine Conjugate beta-Lyase-Dependent Metabolism of Compound A (2-[fluoromethoxy]-1,1,3,3,3-pentafluoro-1-propene) in Human Subjects Anesthetized with Sevoflurane and in Rats Given Compound A

Background: Sevoflurane undergoes Baralyme- or soda lime-catalyzed degradation in the anesthesia circuit to yield compound A (2-[fluoromethoxy]-1,1,3,3,3-pentafluoro-1-propene), which is nephrotoxic in rats and undergoes metabolism via the cysteine conjugate beta-lyase pathway in those animals. The objective of these experiments was to test the hypothesis that compound A undergoes beta-lyase-dependent metabolism in humans.

Methods: Human volunteers were anesthetized with sevoflurane (1.25 minimum alveolar concentration, 3%, 2 l/min, 8 h) and thereby exposed to compound A. Urine was collected at 24-h intervals for 72 h after anesthesia. Rats, which served as a positive control, were given compound A intraperitoneally, and urine was collected for 24 h afterward. Human and rat urine samples were analyzed by19 F nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry for the presence of compound A metabolites.

Results: Analysis of human and rat urine showed the presence of the compound A metabolites [S-[2-(fluoromethoxy)-1,1,3,3,3-pentafluoropropyl]-N-acetyl-L-cysteine, (E)- and (Z)-S-[2-(fluoromethoxy)-1,3,3,3-tetrafluoro-1-propenyl]-N-acetyl-L-cyst eine, 2-(fluoromethoxy)-3,3,3-trifluoropropanoic acid, 3,3,3-trifluorolactic acid, and inorganic fluoride. The presence of 2-(fluoromethoxy)-3,3,3-trifluoropropanoic acid and 3,3,3-trifluorolactic acid in human urine was confirmed by gas chromatography-mass spectrometry.     

Hippocampal Noradrenaline and Serotonin Release over 24 Hours as Measured by the Dialysis Technique in Freely Moving Rats: Correlation to Behavioural Activity State,Effect of Handling and Tail-Pinch

Hippocampal extracellular levels of noradrenaline (NA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) were monitored with the microdialysis technique in freely moving rats. In one experiment 30 min samples were collected during 24 h of continuous perfusion, and the monoamine output was compared to the behavioural activity state, as arbitrarily classified in three categories: sleep/rest, drowsiness and full alertness associated with complex behaviours. In the individual animal the hippocampal NA and 5-HT output showed pronounced fluctuations during the 24 h period, but the 30 min sampling times did not allow for a clear-cut correlation to behavioural activity state. However, the mean NA and 5-HT output for all animals during the dark period of the day was 43 and 38% higher, respectively, than during the light period, and the average NA and 5-HT levels in samples collected during periods of high behavioural activity was 34 and 45% higher, respectively, than during periods of rest or sleep. In contrast, there were no detectable changes in extracellular 5-HIAA. The selective serotonin uptake blocker indalpine, added to the perfusion fluid at 1 microM, increased the extracellular 5-HT levels 6-fold, with a similar correlation to behavioural activity state as without indalpine. In a second experiment the effect of handling and tail-pinch was studied in 15 min sample fractions. Gentle handling of the animals during the sampling period increased the hippocampal NA and 5-HT output by 32 and 72%, respectively, and a similar increase (63 and 48%) was obtained by application of tail-pinch. Maximum NA output was reached during the handling or tail-pinch period, whereas maximal 5-HT levels were detected in the subsequent 15 min sample fraction. No changes in extracellular 5-HIAA was observed. It is concluded (1) that intracerebral microdialysis provides a useful method for the study of extracellular NA and 5-HT in the hippocampal formation of conscious rats during active behaviour; (2) that there are substantial fluctuations in hippocampal NA and 5-HT output in freely moving rats which correlate with the light - dark cycle as well as with the activity state of the animals; (3) that the spontaneous variations in 5-HT output are maintained during reuptake blockade; and (4) that behavioural activation through gentle handling or tail-pinch elicits NA and 5-HT release. The present data support a role of the forebrain NA and 5-HT systems in behavioural state control and highlights the necessity of experimental designs in which the spontaneous fluctuations in transmitter release are controlled for in studies of, for example, drug effects on NA and 5-HT release in conscious animals.     

Effect of a Single Nighttime Dose of Oxazepam on Seizure Duration in Electroconvulsive Therapy

In a double-blind crossover study, 12 depressed inpatients receiving bilateral electroconvulsive therapy (ECT) were given 22.5 mg oxazepam or placebo (identical tablets, randomized order) the night before treatment. Seizure duration was measured using the cuff method and a total of 20 pairs of measurements were made. Mean duration after oxazepam administration was 0.9 s longer than after placebo; this difference was not statistically significant. The relevant lower one-sided 95% confidence limit was -4.1 s. Single administration of oxazepam, 22.5 mg, has little average effect on seizure duration in ECT.     

The Stockholm breast cancer screening trial — 5-year results and stage at discovery

In screening programmes it is important to assess a preliminary effectiveness of the screening method as soon as possible in order to forecast survival figures. In March 1981 a controlled single-view mammographic screening trial for breast cancer was started in the south of Stockholm. The population invited for screening mammography consisted of 40,000 women aged 40–64 years, and 20,000 women served as a well-defined control group. The main aim of the trial was to determine whether repeated mammographic screening could reduce the mortality in the study population (SP) compared to the control population (CP).The cumulative number of advanced mammary carcinomas in the screening and the control populations from the first five years of screening have shown a tendency towards more favourable stages in the screened population aged 40–64 years. A breakdown by age suggests an effect in age group 50–59 years, but not yet in age groups 40–49 and 60–64 years.When comparing the rates of stage II+ cancer, an increased number is found in the study group. As the total rate of breast cancer is higher in SP than in CP, there ought to be a concealed group of stage II+ cancers in the CP which makes the comparison biased. A new approach has been designed, where an estimation of the hidden number of stage II+ cancers in CP is added to the clinically detected cases, and in this respect a comparison has shown a decrease in the cumulative number of advanced cancers in the SP in relation to the CP (p<0.05). According to this it could be important to add the estimated number of undetected, hidden cases in the control group in order to utilize the difference in detection rate in the screening- and control group respectively.     

Increased NADPH-diaphorase activity in canine myxomatous mitral valve leaflets

Comparable pathological changes in the mitral valve have been described in dogs, pigs and human patients with myxomatous mitral valve disease (MMVD), i.e., primary mitral valve prolapse. The progressive myxomatous changes are probably a response to repeated impact on the leaflets, and endothelial stress or damage probably plays a central role in the pathogenesis. Little, however, is known about the vasoactive substances that mediate the subendothelial changes. The aim of this study was to investigate the expression of nitric oxide synthase (NOS) in canine mitral valve leaflets and to relate the findings to MMVD changes. The mitral valve was taken post mortem from 12 dogs (six males and six females) and a whole valve NADPH (the reduced form of nicotinamide-adenine dinucleotide phosphate) diaphorase (NADPH-d) reaction was performed. Macroscopical (semiquantitative) and microscopical (computer image analysis) evaluations of the staining due to NADPH-d activity were performed at four specific areas of the valve and related to microscopical signs of MMVD and gross signs of thickening or prolapse, or both. Macroscopically, the NADPH-d colour grade was correlated with the degree of MMVD (P=0.01). In addition, endothelial NADPH-d staining intensity was correlated with macroscopical signs of disease (P=0.004) as well as with collagen degeneration (P=0.008) and deposition of mucopolysaccharides (P=0.02). Age, gender and specific area of the valve did not seem to influence the NADPH-d activity. In conclusion, increased NADPH-d activity, suggesting increased NOS expression, was found in areas of the mitral valve with myxomatous changes. This indicates that nitric oxide (NO) may play a role in the pathogenesis of MMVD in dogs.     

Band-pass response properties of rat SI neurons

Rats typically employ 4- to 12-Hz "whisking" movements of their vibrissae during tactile exploration. The intentional sampling of signals in this frequency range suggests that neural processing of tactile information may be differentially engaged in this bandwidth. We examined action potential responses in rat primary somatosensory cortex (SI) to a range of frequencies of vibrissa motion. Single vibrissae were mechanically deflected with 5-s pulse trains at rates /=3 Hz. In contrast with this low-pass feature of the response, several other characteristics of the response revealed bandpass response properties. While average evoked response amplitudes measured 0-35 ms after stimulus onset typically decreased with increasing frequency, the later components of the response (>15 ms post stimulus) were augmented at frequencies between 3 and 10 Hz. Further, during the steady state, both rate and temporal measures of neural activity, measured as total spike rate or vector strength (a measure of temporal fidelity of spike timing across cycles), showed peak signal values at 5-10 Hz. A minimal biophysical network model of SI layer IV, consisting of an excitatory and inhibitory neuron and thalamocortical input, captured the spike rate and vector strength band-pass characteristics. Further analyses in which specific elements were selectively removed from the model suggest that slow inhibitory influences give rise to the band-pass peak in temporal precision, while thalamocortical adaptation can account for the band-pass peak in spike rate. The presence of these band-pass characteristics may be a general property of thalamocortical circuits that lead rodents to target this frequency range with their whisking behavior.     

Intranasal immunization of mice with group B streptococcal protein rib and cholera toxin B subunit confers protection against lethal infection

Intranasal immunization of mice with Rib, a cell surface protein of group B streptococcus (GBS), conjugated to or simply coadministered with the recombinant cholera toxin B subunit, induces systemic immunoglobulin G (IgG) and local IgA antibody responses and confers protection against lethal GBS infection. These findings have implications for the development of a human GBS vaccine.