Abnormal reactivity of the approximately 20-Hz motor cortex rhythm in Unverricht Lundborg type progressive myoclonus epilepsy

The approximately 20-Hz component of the human mu rhythm originates predominantly in the primary motor cortex. We monitored with a whole-scalp neuromagnetometer the reactivity of the approximately 20-Hz rhythm as an index of the functional state of the primary motor cortex in seven patients suffering from Unverricht-Lundborg type (ULD) progressive myoclonus epilepsy (PME) and in seven healthy control subjects. In patients, the motor cortex rhythm was on average 5 Hz lower in frequency and its strength was double compared with controls. To study reactivity of the approximately 20-Hz rhythm, left and right median nerves were stimulated alternately at wrists. In controls, these stimuli elicited a small transient decrease, followed by a strong increase ("rebound") of the approximately 20-Hz level. In contrast, the patients showed no significant rebounds of the rhythm. As the approximately 20-Hz rebounds apparently reflect increased cortical inhibition, our results indicate that peripheral stimuli excite motor cortex for prolonged periods in patients with ULD.

[Contamination by helminths in public places of the province of Chubut, Argentina]

Canine-borne helminthiases constitute a worldwide problem. Some of these parasites can originate serious pathologies in humans. Given the potential existence of these zoonoses in Argentina, horizontal surveys on contamination degree evaluated as faeces per hectare and on parasite prevalence in faeces were carried out in six localities of the Province of Chubut. The behaviour of people visiting public places was also analyzed qualitatively. All of the survey sites were contaminated with faeces and with some parasitic forms. Contamination degrees ranged from 32 to 147 faeces/ha. Toxocara sp. (17.4%), Strongyloides sp. (5.1%), and Ancylostoma. sp (5.6%) were the main genera among other parasites detected. As a whole, the analysis revealed that contamination degree, prevalence and human behaviour in relation to the exposure to the parasite would be the main factors to be taken into account in formulating control measures. Transmission risk patterns in Chubut were not homogeneous; therefore, studies and control strategies should be devised and implemented at the local scale.

Position reconstruction from an ensemble of hippocampal place cells: contribution of theta phase coding

Previous analysis of the firing of individual rat hippocampal place cells has shown that their firing rate increases when they enter a place field and that their phase of firing relative to the ongoing theta oscillation (7-12 Hz) varies systematically as the rat traverses the place field, a phenomenon termed the theta phase precession. To study the relative contribution of phased-coded and rate-coded information, we reconstructed the animal's position on a linear track using spikes recorded simultaneously from 38 hippocampal neurons. Two previous studies of this kind found no evidence that phase information substantially improves reconstruction accuracy. We have found that reconstruction is improved provided epochs with large, systematic errors are first excluded. With this condition, use of both phase and rate information improves the reconstruction accuracy by >43% as compared with the use of rate information alone. Furthermore, it becomes possible to predict the rat's position on a 204-cm track with very high accuracy (error of <3 cm). The best reconstructions were obtained with more than three phase divisions per theta cycle. These results strengthen the hypothesis that information in rat hippocampal place cells is encoded by the phase of theta at which cells fire.

Vaccination against cysticercosis and hydatid disease

Infections with the larval stages of taeniid cestode parasites cause substantial human morbidity as well as economic losses in domestic livestock species. Despite ongoing efforts around the world, few countries have been able substantially to reduce or eradicate these infections through the use of anthelmintics and lifestyle changes. Vaccines offer an additional potential tool to assist with the control of parasite transmission. Here, Marshall Lightowlers and colleagues review the substantial progress that has been made towards developing practical vaccines against hydatid disease in sheep and cysticercosis in sheep and cattle. Recombinant antigens have been used to induce more than 90% protection against challenge infections. Such success in animals encourages investigation of the potential use of vaccines in humans to prevent hydatid disease arising from infection with Echinococcus granulosus and cysticercosis from infection with Taenia solium.

Vaccination trials in Australia and Argentina confirm the effectiveness of the EG95 hydatid vaccine in sheep

Experimental vaccine trials against hydatid disease have been undertaken in sheep using the EG95 recombinant vaccine. Challenge infection was with viable Echinococcus granulosus eggs obtained from a New Zealand isolate (dog/sheep cycle), an Australian isolate (dingo/wallaby cycle) and an Argentine isolate (dog/sheep cycle). Vaccination with EG95 conferred a high degree of protection against challenge with all three parasite isolates (protection range 96-100%). Taken together, the trials demonstrated that 86% of vaccinated sheep were completely free of viable hydatid cysts when examined approximately 1 year after challenge infection. Vaccination reduced the number of viable cysts by 99.3% compared with unvaccinated controls. These results suggest that the EG95 vaccine could have wide applicability as a new tool for use in hydatid control campaigns.

An oscillatory short-term memory buffer model can account for data on the Sternberg task

A limited number (7 +/- 2) of items can be held in human short-term memory (STM). We have previously suggested that observed dual (theta and gamma) oscillations could underlie a multiplexing mechanism that enables a single network to actively store up to seven memories. Here we have asked whether models of this kind can account for the data on the Sternberg task, the most quantitative measurements of memory search available. We have found several variants of the oscillatory search model that account for the quantitative dependence of the reaction time distribution on the number of items (S) held in STM. The models differ on the issues of (1) whether theta frequency varies with S and (2) whether the phase of ongoing oscillations is reset by the probe. Using these models the frequencies of dual oscillations can be derived from psychophysical data. The derived values (ftheta = 6-10 Hz; fgamma = 45-60 Hz) are in reasonable agreement with experimental values. The exhaustive nature of the serial search that has been inferred from psychophysical measurements can be plausibly explained by these oscillatory models. One argument against exhaustive serial search has been the existence of serial position effects. We find that these effects can be explained by short-term repetition priming in the context of serial scanning models. Our results strengthen the case for serial processing and point to experiments that discriminate between variants of the serial scanning process.

Extracorporeal membrane oxygenation using a centrifugal pump and a servo regulator to prevent negative inlet pressure

BACKGROUND

We studied whether negative inlet pressure created by a centrifugal pump during extracorporeal membrane oxygenation damages blood.

METHODS

Fresh, whole human blood and primer were circulated through a test circuit, applying an inlet pressure of 0, -50, or -100 mm Hg. Thereafter, hemolysis and kidney function were compared between 6 patients treated before and 14 patients treated after inclusion in our setup of extracorporeal membrane oxygenation with a servo inlet pressure regulator.

RESULTS

In vitro, negative inlet pressure caused substantial hemolysis, leukocyte and platelet destruction, and complement activation. Maximal plasma free hemoglobin concentrations were 199 mg/100 mL before use of the servo inlet pressure regulator and 40 mg/100 mL afterward (p = 0.06), and serum creatinine peaked at 330 and 115 mumol/L, respectively (p = 0.03). The minimal 24-hour diuresis normalized for weight was 4.8 mL/kg before use of the servo inlet pressure regulator and 45.6 mL/kg afterward (p = 0.03). Three of 5 evaluable patients before use of the servo inlet pressure regulator and 1 of 14 patients after inclusion in this setup experienced anuria (p = 0.04).

CONCLUSIONS

There were strong indications that reduction of negative pump inlet pressure with the servo regulator prevented hemolysis and kidney damage.

Temperature guided radiofrequency catheter ablation of myocardium: comparison of catheter tip and tissue temperatures in vitro

Temperature monitoring during RF ablation has been proposed as a means of controlling the creation of the lesion. However, in vivo studies have shown poor correlation between lesion size and catheter tip temperature. Thus, we hypothesized a difference between catheter tip and tissue temperatures during RF catheter ablation, and that this difference may depend on flow passing the ablation site, tip electrode length, and catheter-tissue orientation. In vitro studies were performed using four different ablation catheters (tip electrode length: 2, 4, or 6 mm) with a thermistor or a thermocouple as temperature sensor. Set temperature was 70 degrees C and pulse duration was 30 seconds. Pieces of porcine left ventricle were immersed in a bath of isotonic saline-dextrose solution at 37 degrees C. The ablation catheters were positioned perpendicularly, obliquely, or parallel to the endocardium. A temperature sensor was inserted from the epicardial side and positioned 1 mm beneath the catheter-tissue interface. Experiments were made with a flow of 200 mL/min passing the ablation site or with no flow. The catheter tip and tissue temperatures differed significantly (P < 0.0001) during ablation. This difference increased with time, with flow passing the ablation site, with the length of the tip electrode, and when the catheter was positioned perpendicularly or obliquely to the endocardium as compared to the parallel catheter-tissue orientation (P < 0.05). In conclusion, the tissue temperature may far exceed the catheter tip temperature, and intramyocardial superheating resulting in steam formation and popping may occur despite a relatively low catheter tip temperature.

Hippocampal CA3 region predicts memory sequences: accounting for the phase precession of place cells

Hippocampal recordings show that different place cells fire at different phases during the same theta oscillation, probably at the peak of different gamma cycles. As the rat moves through the place field of a given cell, the phase of firing during the theta cycle advances progressively. In this paper we have sought to determine whether a recently developed model of hippocampal and cortical memory function can explain this phase advance and other properties of place cells. According to this physiologically based model, the CA3 network stores information about the sequence of places traversed during learning. Here we show that the phase advance can be understood if it is assumed that the hippocampus is in a recall mode that operates when the animal is already familiar with a path. In this mode, sensory information about the current position triggers recall of the upcoming 5-6 places (memories) in the path at a rate of one memory per gamma cycle. The model predicts that the average phase advance will be one gamma cycle per theta cycle, a value in reasonable agreement with the data. The model also correctly accounts for (1) the fact that the firing of a place cell occurs during approximately 7 theta cycles (on average) as the animal crosses the place field; (2) the observation that the phase of place cell firing depends more systematically on position than on time; and (3) the fact that traversal of an already familiar path produces further modifications (shifts the firing of a cell to an earlier position in the path). This later finding suggests that recall of previously stored information strengthens the memory of that information. In the model, this occurs because of a novel role of N-methyl-D-aspartate channels in recall. The general success of the model provides support for the idea that the hippocampus stores sequence information and makes predictions of expected positions during gamma-frequency recall.

Physiologically realistic formation of autoassociative memory in networks with theta/gamma oscillations: role of fast NMDA channels

Recordings from brain regions involved in memory function show dual oscillations in which each cycle of a low-frequency theta oscillation (5-8 Hz) is subdivided into about seven subcycles by high frequency gamma oscillations (20-60 Hz). It has been proposed (Lisman and Idiart 1995) that such networks are a multiplexed short-term memory (STM) buffer that can actively maintain about seven memories, a capability of human STM. A memory is encoded by a subset of principal neurons that fire synchronously in a particular gamma subcycle. Firing is maintained by a membrane process intrinsic to each cell. We now extend this model by incorporating recurrent connections with modifiable synapses to store long-term memory (LTM). The repetition provided by STM gradually modifies synapses in a physiologically realistic way. Because different memories are active in different gamma subcycles, the formation of autoassociative LTM requires that synaptic modification depend on N-methyl-D-aspartate (NMDA) channels having a time constant of deactivation that is of the same order as the duration of a gamma subcycle (15-50 msec). Many types of NMDA channels have longer time constants (150 msec), as for instance those found in the hippocampus, but both fast and slow NMDA channels are present in cortex. This is the first proposal for the special role of these fast NMDA channels. The STM for novel items must depend on activity-dependent changes intrinsic to neurons rather than recurrent connections, which have not developed the required selectivity. Because these intrinsic mechanisms are not error-correcting, STM will become slowly corrupted by noise. This limits the accuracy with which LTM can become encoded after a single presentation. Accurate encoding of items in LTM can be achieved by multiple presentations, provided different memory items are presented in a varied interleaved order. Our results indicate that a limited memory-capacity STM model can be integrated in the same network with a high-capacity LTM model.

Novel lists of 7 +/- 2 known items can be reliably stored in an oscillatory short-term memory network: interaction with long-term memory

This paper proposes a model for the short-term memory (STM) of unique lists of known items, as, for instance, a phone number. We show that the ability to accurately store such lists in STM depends strongly on interaction with the preexisting long-term memory (LTM) for individual items (e.g., digits). We have examined this interaction in computer simulations of a network based on physiologically realistic membrane conductances, synaptic plasticity processes, and brain oscillations. In the model, seven STMs can be kept active, each in a different gamma-frequency subcycle of a theta-frequency oscillation. Each STM is maintained and timed by an activity-dependent ramping process. LTM is stored by the strength of synapses in recurrent collaterals. The presence of preexisting LTM for an item greatly enhances the ability of the network to store an item in STM. Without LTM, the precise timing required to keep cells firing within a given gamma subcycle cannot be maintained and STM is gradually degraded. With LTM, timing errors can be corrected and the accuracy and order of items is maintained. This attractor property of STM storage is remarkable because it occurs even though there is no LTM that identifies which items are on the list or their order. Multiple known items can be stored in STM, even though their representation is overlapping. However, multiple, identical memories cannot be stored in STM, consistent with the psychophysical demonstration of repetition blindness. Our results indicate that meaningful computation (memory completion) can occur in the millisecond range during an individual gamma cycle.

Theta/gamma networks with slow NMDA channels learn sequences and encode episodic memory: role of NMDA channels in recall

This paper examines the role of slow N-methyl-D-aspartate (NMDA) channels (deactivation approximately 150 msec) in networks that multiplex different memories in different gamma subcycles of a low frequency theta oscillation. The NMDA channels are in the synapses of recurrent collaterals and govern synaptic modification in accord with known physiological properties. Because slow NMDA channels have a time constant that spans several gamma cycles, synaptic connections will form between cells that represent different memories. This enables brain structures that have slow NMDA channels to store heteroassociative sequence information in long-term memory. Recall of this stored sequence information can be initiated by presentation of initial elements of the sequence. The remaining sequence is then recalled at a rate of one memory every gamma cycle. A new role for the NMDA channel suggested by our finding is that recall at gamma frequency works well if slow NMDA channels provide the dominant component of the EPSP at the synapse of recurrent collaterals: The slow onset of these channels and their long duration allows the firing of one memory during one gamma cycle to trigger the next memory during the subsequent gamma cycle. An interesting feature of the readout mechanism is that the activation of a given memory is due to cumulative input from multiple previous memories in the stored sequence, not just the previous one. The network thus stores sequence information in a doubly redundant way: Activation of a memory depends on the strength of synaptic inputs from multiple cells of multiple previous memories. The cumulative property of sequence storage has support from the psychophysical literature. Cumulative learning also provides a solution to the disambiguation problem that occurs when different sequences have a region of overlap. In a final set of simulations, we show how coupling an autoassociative network to a heteroassociative network allows the storage of episodic memories (a unique sequence of briefly occurring known items). The autoassociative network (cortex) captures the sequence in short-term memory and provides the accurate, time-compressed repetition required to drive synaptic modification in the heteroassociative network (hippocampus). This is the first mechanistically detailed model showing how known brain properties, including network oscillations, recurrent collaterals, AMPA channels, NMDA channel subtypes, the ADP, and the AHP can act together to accomplish memory storage and recall.

Aflatoxin B1 induced lacI mutation in liver and kidney of transgenic mice C57BL/6N: effect of phorone

Transgenic C57BL/6N mice containing a lambda shuttle vector carrying a lacI target and an alpha-lacZ reporter gene have been used to study the modulating effect of phorone, a glutathione-depleting agent, on the mutagenic activity of aflatoxin B1 (AFB1) in vivo. Animals were treated with AFB1 (8 mg/kg) for four consecutive days and the animals sacrificed 21 days after the last treatment. Treatment with AFB1 alone did not result in a significant increase in mutation frequency in the liver and kidney. When the animals were treated with phorone 4 h prior to treatment with AFB1 a significant increase in mutation frequency was observed in the liver (4-fold) and kidney (1.5-fold). Phorone treatment did not increase the AFB1-induced mutation frequency in the lung and intestine. DNA sequence analyses of 30 independent clones isolated from the liver of AFB1-treated animals showed that G:C --> T:A transversion (60%) was the predominant mutational event. Mutations within the lacI gene could not be detected in seven of 30 mutants. The mutations were randomly distributed throughout the coding sequences of the lacI gene and no hotspots for the mutations were observed. However, codons 86 and 928 appeared to be major sites for mutation. The study shows that the transgenic mouse in vivo mutagenesis model can be used to study the influence of effect-modifying compounds on the mutagenic activity of known carcinogens.

Imaging of chondrosarcoma with histopathological and prognostic correlation. An analysis of 49 cases mainly based on plain film radiography

PURPOSE

To investigate the course of chondrosarcoma in relation to radiographic and histopathologic findings.

MATERIAL AND METHODS

49 consecutive patients seen during an 11-year-period were analysed, including re-evaluation of their radiographic and histopathologic material.

RESULTS

Forty-two patients had radiographic changes typical for cartilaginous tumours, in 37 with malignant stigmata. Seven patients had malignant changes not typical for chondrosarcoma. By histopathologic grading 16 patients had grade I, 17 grade II and 16 grade III tumours. Six of the grade II-III tumours were histopathologic variants (mesenchymal, dedifferentiated or myxoid chondrosarcomas). Surgical removal of the tumour was performed in 42 patients, 41 of whom were followed up for 0.4-11.4 years (median 3.8 years). Local recurrence occurred in 7 patients, and 11 patients developed metastases. Ten patients, 4 with local recurrence and metastases, and 6 with metastases only were dead at the end of the follow-up. The actuarial 5-year overall survival rate was 64%. The occurrence of local recurrence, metastases and death was found to be related to the histopathologic grades II and III. Atypical radiographic features only occurred in grade II-III tumours and were related to metastases and death, but not to local recurrence.

CONCLUSION

Atypical radiographic findings were related to high-grade malignancy and poor prognosis.

[Occupational accidents in the fishing industry. A survey of fishing-related accidents treated at the Bornholm Central Hospital in Rønne as well as in general practice 1987-1990]

Over a two year period from 1987-1989 all fishing-related injuries treated in the Emergency Room at Bornholm's central hospital in Rønne and at some general practices were registered prospectively. One hundred injuries were registered altogether. Accidents occurring in connection with putting out and recovering apparatus constituted respectively 14% and 36%. Working with the trawler scoop was responsible for 18% of the accidents and was the most common direct cause, followed by work with winches which constituted 11%. Falls made up almost a quarter of the accidents. Finger injuries constituted 33%, and hand and wrist injuries 17%. Trawler scoop injuries most commonly involved the fingers and hands and fish-cleaning injuries the hands, wrists and fingers. Prophylactic efforts concerning safety in work with trawler scoops, winches and steering systems should be made.

A pressure-recording guide wire for measurements of trans-stenotic gradients in arteries. In vitro validation

RATIONALE AND OBJECTIVES

A 0.018'' guide wire with a pressure sensor near the tip has been developed for measuring arterial trans-stenotic pressure gradients. The pressure-recording properties of this system in vitro are evaluated.

METHODS

Static and dynamic tests were performed with five guide wires. Dynamic tests (step response and recordings of phase and frequency response) were performed with a pressure generator connected to a recording system and a spectrum analyzer.

RESULTS

Zero drift at 3 hours ranged from -1.9 to 2.2 mmHg/hour. Sensitivity drift ranged from 0.3% to 2.1%/hour. Hysteresis ranged from 0.2% to 4.3% (mean 2.4%). Bending in arcs of 180 degrees with diameters < 4 cm changed sensitivity and zero pressure recordings in all guide wires. Dynamic recordings showed a slight undershoot and no oscillation.

CONCLUSION

Static errors exceeded those of external pressure transducers for fluid-filled catheters, indicating suboptimal recordings of absolute pressures. However, the small size, and the good dynamic properties, make this pressure wire a promising device for recording trans-stenotic pressure gradients in arteries.

Theory and measurements of snores

Upper airway narrowing, collapsibility, and resistance are recognized predisposing factors for snoring and obstructive sleep apnea, but the mechanisms of their action and interaction are not known. We studied a simple theoretical model of the upper airways, consisting of a movable wall in a channel segment that connects to the airway opening via a conduit with a resistance. Inspiratory flow (V) through the channel segment causes local pressure changes due to viscous losses and the Bernoulli force that may overcome the elastic forces acting on the movable wall. The model predicts instability leading to upper airway closure over a wide range of parameter values. Increasing inspiratory V above a boundary, determined by values of upper airway resistance, segment compliance, length, width, and diameter, as well as gas density, leads to a dynamic airway closure. The mathematical model establishes the power relationships between parameters and provides physiologically realistic quantitative simulation of upper airway closure when values are adapted from literature and from radiographic measurements of upper airway motion induced by negative pressure. The rate of appearance of repetitive sound structures during snoring was favorably compared with the model's prediction of the time course of wall motion during collapse. V measurements during simulated snores revealed an asymmetric oscillatory pattern compatible with repetitive upper airway closure. We conclude that snoring may be modeled as a series of dynamic closure events of the upper airways. The model predicts that the width and length of the movable portion of the upper airways and the gas density are likely to affect the onset of snoring, in addition to other, previously recognized, parameters.

A training simulator for detecting equipment failure in the anaesthetic machine

Simulation is often used for training personnel in activities where the consequences of inappropriate actions are serious. We report a realistic training simulator, which can reproduce practically all potential malfunctions in the anaesthetic machine. Using actual standard equipment (Dameca 10750), the interior of the anaesthetic machine has been profoundly modified, whereas the external appearance remains virtually unchanged. The concealed alterations allow 20 different pre-set technical faults to be activated selectively from a mobile control unit. While assisted by an instructor, the trainee performs hands-on interactive experimentation with the simulator, while being exposed to 'unexpected' machine faults, which prompt for interpretation of error symptoms. Alternatively, the trainee can personally activate the simulated symptoms of different component failures, to enhance learning of the functional principles of the apparatus. The latter approach also allows a systematic presentation of defects to be identified by each step in a formal safety checklist for anaesthetic machines.

[New electronic methods for clinical measurement of temperature]

A proposed Norwegian ban on clinical thermometers containing mercury will affect the equipment available for clinical measurements of temperature. The basic technological principles and applications of electronic thermometers and infrared tympanic thermometers are reviewed and discussed.

[Caustic injuries of the esophagus]

Several different agents can cause lesions of the esophagus if they are ingested. An esophagoscopy is necessary for proper evaluation of the damage. Our experience over the last 12 years substantiates that lye and strong alkalis are the most dangerous substances to swallow. The decision to do an esophagoscopy should be based on certain criteria listed in the paper.

Site classification for the osseointegrated implant

Descriptions of jaw anatomy and bone quality have been based on total jaw resorption classifications. These classifications have not been specific for treatment planning for the osseointegrated implant. The proposed classification describes specific sites by bone quantity and quality and proximity to vital structures. This classification is suggested as an aid in assigning a prognostic value to implants and for the purpose of clarity and communication between the various dental disciplines.

A method for objective measurement of fetal head compression during the second stage of labor

The article describes a novel method for the objective measurement of compression forces to which the fetal head is exposed during labor. This involves the placement of a transducer, housed in a silicone rubber and brass casing (18 mm diameter, 6.5 mm thick), over the parietal bone area. The compression forces monitored with the transducer in this position provide an estimate of the intracranial pressure. The technique thus not only provides a means of assessing fetal head compression, but also the efficacy of the expulsion efforts of the mother. Pressure recordings taken during the second stage of 24 deliveries revealed a marked variation in the magnitude of the compression forces between the births.

Monophasic action potentials in patients with coronary artery disease: reproducibility and electrical restitution and conduction at different stimulation rates

Monophasic action potentials were recorded in the outflow tract of the right ventricle in patients with coronary artery disease during ventricular pacing at different basic cycle lengths and programmed stimulation. During continuous pacing (basic cycle length 600 ms) the time for 90% repolarisation (MAP90) and the QTa interval decreased exponentially during the first 1.5-2 min of pacing to 90% of control values. The reproducibility of the monophasic action potential signals and the ventricular effective refractory period were assessed as good when studied after repetitive trains of 8 beats for more than 1.5 min. The reproducibility of conduction, however, was less good. Electrical restitution of MAP90 duration of the premature beats determined at three different basic cycle lengths was different from that in single muscle preparations. The curves showed two phases with unchanged MAP90 durations despite longer coupling intervals. The first phase was close to the ventricular effective refractory period, probably because subnormal conduction left the diastolic interval constant for the earliest premature beats. This indicates that subnormal conduction may influence the premature dispersion of repolarisation.

Inferior alveolar nerve repositioning in conjunction with placement of osseointegrated implants: a case report

A procedure for relocation of the inferior alveolar nerve to facilitate placement of endosseous implants is described. The technique permits placement of implants in an atrophied mandibular alveolar ridge that lacks sufficient vertical height superior to the mandibular canal. Placement of a fixed prosthesis instead of a removable appliance is facilitated.

Neonatal retinal hemorrhages and neurobehavior related to tractive force in vacuum extraction

Fifty clinically indicated vacuum extractions were studied to evaluate a possible relationship between neurobehavioral abnormality, retinal hemorrhages and the tractive force used for delivery. A Vacuum Extractor Recorder (Type SF 30, Knick), was used to measure the forces necessary for delivery of the head. Infants delivered by the use of extensive tractive force showed no greater incidence of neuropathology than those delivered with less tractive force. The retinal hemorrhages were equally distributed among the infants, irrespective of the tractive force applied or the neurobehavioral assessment. The implication is that retinal hemorrhages cannot be used to evaluate the extent of cerebral influence after birth and that the main cause of neurobehavioral abnormality is the condition leading to the use of the vacuum extractor (VE).

Application of fiberoptics to the clinical measurement of intra-uterine pressure in labor

In the present report we describe a new technique for monitoring intra-uterine pressures during labor. The method utilizes a fiberoptic pressure transducer which is both accurate and stable. The pressure sensor is located at the catheter tip thus eliminating hydrostatic errors during monitoring. At body temperature the catheter is soft and flexible and represents no harm to the fetus. The membrane is housed in a metal dome with large lateral apertures. This arrangement greatly reduces the possibility of blockage. A comparison was made between recordings from the fiberoptic pressure transducer and those from a fluid-filled catheter implanted simultaneously in non-selected subjects during labor. Close agreement was obtained in the majority of cases. Large discrepancies between the two techniques were assumed to reflect the fact that the precise measuring point is not identical in each system. To date, recordings have been made in 52 parturients with no problems with insertion of the device and without any indication of equipment malfunction.

Intramuscular fluid pressure during isometric contraction of human skeletal muscle

Intramuscular fluid pressures were recorded in the vastus medialis of seven healthy male volunteers. Pressures were measured simultaneously at three different sites in the muscle by a catheter-tip transducer with extremely low volume-displacement characteristics and by two extracorporeal transducers connected to slit catheters. All three recording systems gave qualitatively similar results provided the catheters had inner diameters exceeding 0.53 mm and allowed measurement of pressures lasting as short as 1 s. Wick catheters yielded slower responses than slit catheters. At any position intramuscular fluid pressure increased linearly with force up to maximal voluntary contraction (MVC). However, slopes of these curves varied greatly mainly because the pressure was also a linear function of the distance from the fascia. The highest recorded pressure was 570 Torr. At prolonged submaximal contractions intramuscular fluid pressure oscillated independent of contraction force. The linearity of both the pressure-force relationship and the pressure-depth relationship is compatible with a simple model based on the law of Laplace because the muscle fibers are curved during contraction in this muscle. It is hypothesized that blood flow is first compromised deep in the muscle where pressure is highest and in general at lower stress or tension in short bulging muscles with great curvature of the fibers compared with long slender ones.

[The autoinoculation test. False-positive reactions caused by herpes simplex virus]

The autoinoculation test has been used as a diagnostic procedure in patients with chancroid-suspected genital ulcerations. In four of 13 patients with a positive autoinoculation test, herpes simplex virus type 2 was isolated from the primary lesions. In two of the cases this virus was also isolated from the inoculation site, and one patient developed a recurrent herpetic eruption here. Two patients were proven to have chancroid. Three of the remaining seven patients developed recurrent herpes genitalis later. It is concluded that the autoinoculation test should be avoided as a diagnostic procedure because of lack of specificity and risk of inducing recurrent herpes simplex at the site of inoculation.

Prevention of pressure sores by identifying patients at risk

The risk of pressure sores developing in patients admitted with acute conditions was assessed by a simple risk score system based on age, reduced mobility, incontinence, pronounced emaciation, redness over bony prominences, unconsciousness, dehydration, and paralysis in a prospective clinical study. During seven months in 1977, 600 of 3571 patients were classified as at risk. Of these 35 (5.8%) developed sores compared with five (0.2%) of those not at risk. The results of this study compared with those over the same period in 1976 show that close observation of at-risk patients and early detection of pressure sores prevents their development.

Osteitis in early syphilis. A case report

Osteitis of the tibia was diagnosed in a patient presenting with secondary syphilis. The course of the illness indicates that pain in bones in secondary syphilis may be the first symptom of an otherwise inapparent osteitis.

Contact allergy to propylene oxide and isopropyl alcohol in a skin disinfectant swab

Two laboratory assistants developed contact dermatitis from a disposable swab for pre-injection use, containing isopropyl alcohol 70% and propylene oxide 1%. Patch testing gave position allergic reactions to propylene oxide in both patients, one of whom also reacted to isopropyl alcohol. Testing of 25 control persons gave negative results.

White fingernails preceded by multiple transverse white bands

In a patient with hepatocellular damage due to abuse of alcoholic liquors, multiple transverse white bands were found in all fingernails. On examination 3 months later the bands had disappeared, and the nails had developed into typical white nails. The changes were located in the nail bed, and were possibly caused by vascular alterations.

Pyriderm shampoo in the treatment of Pediculosis capitis

112 patients with head lice were treated with a shampoo containing pyrethrins. All were treated twice with an interval of one week. At examination immediately before the second treatment, 6 patients had small, newly hatched lice, and one patient had both small and mature lice--probably due to reinfestation. This patient was lice-free after the third treatment, the other patients after the second treatment. It is concluded that pyrethrins are highly effective against head lice and have the advantages of a low toxicity to mammals and a short contact time.

Contact sensitization to benzoyl peroxide following topical treatment of chronic leg ulcers

Sixteen patients with chronic leg ulcers were treated with 10% benzoyl peroxide gel for 6 weeks. At the end of the treatment, patch tests with 2% benzoyl peroxide in petrolatum and 10% in a gel showed that nine patients (56%) had become sensitized. This high sensitization rate is in good accord with the results obtained by experimental investigations using human maximization tests and repeated insult patch tests. A strong sensitizer such as benzoyl peroxide should not be used in the routine treatment of chronic leg ulcers, despite its good healing effect.