Correlative physiological and morphological studies of rapidly adapting mechanoreceptors in cat's glabrous skin

1. A total of fifty-four mechanoreceptor afferent units with fast conducting axons in the tibial nerve innervating the glabrous skin of the hind leg were isolated in anaesthetized cats. 2. Twenty-six rapidly adapting units (RA), eighteen slowly adapting units (SA) and ten Pacinian corpuscle units (PC) were differentiated from each other mainly on the presence of the off response in RA and PC units to a ramp stimulation, the persistence of discharges of the SA units during steady pressure on the receptive field and the classical tuning curve seen in the PC units. A few PC units in the hairy skin were also studied for comparison. 3. Lamellated corpuscles were found histologically in the skin of the receptive field of RA units and identified as Krause's corpuscle of cylindrical type by their superficial location in the cutaneous tissue and their structure revealed by electron microscopy. 4. Physiological characteristics of RA units to various forms of mechanical stimulation were studied and compared with those of the other two kinds of units. SA units had the lowest critical slope among three groups and PC units the highest. 5. The discharge pattern of RA and PC units to a ramp stimulation was found to be time-locked, whereas with SA unites only the first spike appeared at a fixed latency from the start of stimulation. 6. Some RA units showed a tuning curve which was flat from 10 to 200 Hz. Those with narrowly tuned curves had a best turning frequency at around 20 Hz. They were easily differentiated from the SA and PC units. SA units were tuned best at 5 HZ or less, and PC units at around 200 HZ. 7. The relation between the indentation velocity and amplitude of the ramp and the spike discharges was analysed in eleven RA units. In most cases the relation between identation velocity and maximum instataneous frequency was found to be best fit with a power function although other kinds of functions (linear, logarithmic, and logarithmic hyperbolic tangent) could also fit the relation at the 1% significance level. The instantaneous impuse frequency in RA units in response to various indentation amplitudes showed a step function. 8. The "off" responses to a ramp stimulation in RA units were also analysed in detail.     

Pathway and speed of calcium movement from blood to mineralizing enamel

We studied by autoradiography the distribution of 45Ca in the enamel organ of frozen rats 4.3, 6.1, 7.8, 10.6 and 13.7 sec after an i.v. injection. The intercellular junctions of the proximal side of the smooth-ended ameloblast (SA) and the distal side of the ruffle-ended ameloblast (RA) were closed to calcium. The junctions of the distal side of SA, the proximal side of RA, and both sides of the secretory stage ameloblasts were not. The time required for calcium to pass through the ameloblast layer was less than 1.8 sec in the secretory stage and SA region. The time in the RA region was 3.5-6.3 sec. In the transitional region from RA to SA, a band of strong radioactivity appeared from the papillary layer of RA region towards the enamel of the SA region. The radioactivity in the secretory stage enamel increased almost linearly with time. The diffusion speed of calcium in the enamel was more than 50 microns for 1.8 sec in the maturation stage and less than 15 microns for 9.4 sec in the secretory stage. These results indicate that in the secretory and SA regions calcium moves to the enamel surface through the intercellular spaces of ameloblasts and in the RA region via RA cells.     

Receptive properties of mouse sensory neurons innervating hairy skin

Using an in vitro nerve skin preparation and controlled mechanical or thermal stimuli, we analyzed the receptive properties of 277 mechanosensitive single primary afferents with myelinated (n = 251) or unmyelinated (n = 26) axons innervating the hairy skin in adult or 2-wk-old mice. Afferents were recorded from small filaments of either sural or saphenous nerves in an outbred mice strain or in the inbred Balb/c strain. On the basis of their receptive properties and conduction velocity, several receptor types could be distinguished. In adult animals (>6 wk old), 54% of the large myelinated fibers (Abeta, n = 83) showed rapidly adapting (RA) discharges to constant force stimuli and probably innervated hair follicles, whereas 46% displayed a slowly adapting (SA) response and probably innervated Merkel cells in touch domes. Among thin myelinated fibers (Adelta, n = 91), 34% were sensitive D hair receptors and 66% were high-threshold mechanoreceptors (AM fibers). Unmyelinated fibers had high mechanical thresholds and nociceptive functions. All receptor types had characteristic stimulus-response functions to suprathreshold force stimuli. Noxious heat stimuli (15-s ramp from 32 to 47 degrees C measured at the corium side of the skin) excited 26% (5 of 19) of AM fibers with a threshold of 42.5 +/- 1.4 degrees C (mean +/- SE) and an average discharge of 15.8 +/- 9.7 action potentials and 41% (7 of 17) C fibers with a mean threshold of 37.6 +/- 1.9 degrees C and an average discharge of 22.0 +/- 6.0 action potentials. Noxious cold stimuli activated 1 of 10 AM fibers and 3 of 10 C fibers. One of 10 C units responded to both heat and cold stimuli. All types of afferent fibers present in adult mice could readily be recognized in mice at postnatal day 14. However, fibers had reduced conduction velocities and the stimulus-response function to mechanical stimuli was more shallow in all fibers except for the D hairs. In juvenile mice, 22% of RA units also displayed an SA response at high stimulus intensities; these units were termed RA/SA units. We conclude that all types of cutaneous afferent fibers are already committed to their phenotype 2 wk after birth but undergo some maturation over the following weeks. This preparation has great potential for the study of transgenic mice with targeted mutations of genes that code factors that are involved in the specification of sensory neuron phenotypes.     

Modulation of human stratum corneum properties by salicylic acid and all-trans-retinoic acid

Topical all-trans-retinoic acid (RA) has been reported to decrease the in vivo skin response to sodium lauryl sulfate (SLS). The converse was also shown with a synergistic effect of RA following prior applications of SLS. The reason for such effects is not clear. We employed measures of transepidermal water loss (TEWL), squamometry and sequential corneosurfametry to explore the protective activity of a 0.05% RA cream at the level of the stratum corneum. Nonionic oil-in-water emulsions with or without 5% salicylic acid (SA) served as test product references. Data indicated that the RA formulation was responsible for a stochastic impairment in the TEWL and for an increased intercorneocyte cohesion. SA and the unmedicated emulsion did not lead to similar TEWL changes. The squamometry test proved to be very sensitive to disclose the effects of SA and RA without, however, allowing to distinguish the difference in the physiological processes involved. The corneosurfametry bioassay did not show any protection or synergistic effect between RA or SA and SLS challenge on the stratum corneum. This is in contrast to a previous work showing a positive protective effect afforded by retinol against SLS. The combined effects of irritant compounds affecting the stratum corneum are complex. The precise reason for some of their biological consequences remains a conundrum. On balance, products such as SA and RA do not appear to afford protection or impairment to a surfactant challenge at the level of the stratum corneum.     

Velocity of peristaltic propagation in distal esophageal segments

Recent studies of the peristaltic pressure wave have suggested the presence of two sequential but overlapping contraction segments in the distal esophageal body. In this report, propagation velocity of esophageal peristalsis was determined in these segments in normal subjects (N = 35) and in patients with high-amplitude peristalsis (nutcracker esophagus, N = 25) to see if intersegment differences were present in the normal or abnormal setting. Velocity measurements were made from conventional manometric tracings in two 4-cm regions representing the distal smooth-muscle segments. A novel method of velocity measurement was employed that used regression lines established from contraction onset times. In normal subjects, propagation velocity decreased significantly from the proximal to distal segment (4.9 +/- 0.5 cm/sec, vs 3.2 +/- 0.2 cm/sec, P < 0.01). Velocity also decreased across segments in nutcracker-esophagus patients (5.3 +/- 0.6 cm/sec, vs 3.6 +/- 0.7 cm/sec, P = 0.06), but the difference reached statistical significance only when the subset with highest amplitudes (> or = 180 mm Hg) was analyzed separately. Greater variance in velocity in the distal smooth-muscle segment of nutcracker-esophagus patients (P < 0.01) was, in part, responsible for this statistical observation. We conclude that normal propagation velocity decreases across regions corresponding to the smooth-muscle contraction segments defined by recent studies of peristalsis, supporting the assumption that they represent separate neuromuscular units. The mechanisms responsible for contraction wave abnormalities in the nutcracker esophagus have a minimal effect on propagation velocity, an effect that is restricted to the distal smooth-muscle segment of the esophageal body.     

Coherence thresholds for discrimination of motion direction in infants

The sensitivity of 3-month-old infants to direction of motion in random-dot patterns was assessed by measuring coherence thresholds for the discrimination of a pattern, in which opposite directions were segregated into alternate horizontal strips, from an unsegregated pattern. The coherently moving dots had a displacement size of 0.16 deg (velocity 8 deg/sec), and their direction of motion reversed periodically. For both infants and an adult subject coherence thresholds decreased with increasing height of the segregated strips, and with increasing duration of the interval between direction reversals. However the infants required larger minimum heights and longer minimum durations in order to extract motion direction. Even under the best conditions infants were markedly less sensitive, with coherence thresholds of around 50%, compared with 5-7% for the adult. In addition, within the group of infants coherence thresholds were negatively correlated with age. This developmental increase in motion sensitivity at an intermediate velocity suggests that a large part of the improvement in upper and lower velocity thresholds during development is a result of a uniform increase in sensitivity across all velocities, though the results do not rule out additional specific improvements in sensitivity at the extremes of the velocity range.     

Blink reflex recovery cycle in patients with blepharospasm unilaterally treated with botulinum toxin

To study the role of arterial blood dynamics in the thrombogenesis of thrombin-induced experimental retinal vein obstruction, the retinal blood flow velocity was evaluated using scanning laser ophthalmoscopic fluorescein videoangiography in an experimental rabbit retinal vein obstruction model. Retinal vein obstruction was made by transadventitial direct instillation of thrombin to the retinal vessels from the vitreous side. The blood flow velocity in the retinal artery and vein was estimated by measuring the passing velocity of the flow head of the dye bolus and venous filling time, respectively. 23 animals were treated with thrombin and compared with 18 controls not treated. In the control group retinal artery blood flow velocity and retinal venous fluorescein filling time was 5.3 +/- 1.1 mm/sec (mean +/- standard deviation) and 6.2 +/- 1.2 sec, respectively. In the treated group the values were 5.7 +/- 1.3 mm/sec and 5.8 +/- 1.0 sec before the thrombin administration, and 3.0 +/- 0.9 mm/sec at 24 hours after its administration, and 5.7 +/- 2.0 sec and 4.0 +/- 1.5 mm/sec and 4.5 +/- 1.4 sec at 48 hours after the administration. These results indicate that a decrease in retinal artery blood flow velocity is strongly involved in the thrombogenesis in thrombin-induced experimental retinal vein obstruction.     

Encoding of shape and orientation of objects indented into the monkey fingerpad by populations of slowly and rapidly adapting mechanoreceptors

The peripheral neural representation of object shape and orientation was studied by recording the responses of a spatially distributed population of rapidly and slowly adapting type I mechanoreceptors (RAs and SAs, respectively) to objects of different shapes and orientations indented at a fixed location on the fingerpad of the anesthetized monkey. The toroidal objects had a radius of 5 mm on the major axis, and 1, 3, or 5 mm on the minor axis. Each object was indented into the fingerpad for 4 s at orientations of 0, 45, 90, and 135 degrees using a contact force of 15 gwt. Estimations of the population responses (PRs) were constructed by combining the responses of 91 SA and 97 RA single afferents at discrete times during the indentation. The PR was composed of the neural discharge rates (z coordinate) plotted at x and y coordinates of the most sensitive spot of the receptive field. The shapes of the PRs were related to the shapes of the objects by fitting the PRs with Gaussian surfaces. The orientations of the PRs were determined from weighted principal component analyses. The SA PR encoded both the orientation and shape of the objects, whereas the RA PR did neither. The SA PR orientation was biased toward the long axis of the finger. The RA PR encoded orientation only for the object with the highest curvature but did so ambiguously. Only the SA PR was well fit by a Gaussian surface. The shape of the object was discriminated by the SA PR within the first 500 ms of contact, and the form of the SA PR remained constant during the subsequent 3.5 s. This was manifested by constant widths of the PR along the major and minor axes despite a peak response that decreased from its maximum at 200 ms to an asymptotic value starting at 1 s. Thus the shape and orientation of each object were coded by the shape and orientation of the SA PR.     

Characterization of heterologously expressed recombinant retinoic acid receptors with natural or synthetic retinoids

The first step in retinoid action is binding to their nuclear receptors. Therefore, characterization of binding characteristics of retinoids is of major importance. Human retinoic acid receptors alpha (hRAR alpha), hRAR beta, and mouse RAR gamma (mRAR gamma) were expressed heterologously in Escherichia coli as a recombinant glutathione S-transferase (GST) fusion protein. The expressed fusion proteins were functional and bound specifically to the all-trans-retinoic acid (RA). The dissociation constants (Kd) for RA were 1.4 nM for GST-hRAR alpha, 1.4 nM for GST-hRAR beta, and 3.3 nM for GST-mRAR gamma, respectively. The fusion proteins were further used for competitive displacement assays to determine the displacement constant (DC50) for other selected retinoids. All-trans-RA and 4-oxo-all-trans-RA have high affinity with all three receptors (DC50 = 0.8-55 nM). The 13-cis RA binds to hRAR alpha with low affinity, but not to other RARs evaluated here. All-trans-N-ethylretinamide, all-trans-retinylacetate, and an ethyl ester of tetrahydronaphthalene derivative had no affinity to any RARs. The hRAR alpha and mRAR gamma receptors did not bind a naphthalene carboxylic acid derivative of RA, but hRAR beta binds this chemical with high affinity. Results indicated that the three recombinant proteins were functional in binding various RA congeners. The affinity and binding data of these retinoids were compared to their observed teratogenic activity.     

Investigation in real time of the effect of gravitation on human spermatozoa and their tendency to swim-up and swim-down

The purpose of this study was to investigate the laterality of muscle fiber conduction velocity in biceps brachii for badminton players, who have stronger arm in the handedness side for long term training. The muscle fiber conduction velocity was calculated from the propagation time of the action potentials along the muscle fibers and the electrode separation using cross-correlation method. For badminton players, significant lateral differences (e.g. right side skillful) were observed in the upper arm girth (P < 0.01) and isokinetic peak torque at 0, 10, 20, 30, 40 rpm (P < 0.01). For control subjects, significant lateral differences were in upper arm girth (P < 0.05) and isokinetic peak torque at exactly 30 rpm (P < 0.05). As for muscle fiber conduction velocity, there were no statistically significant differences between right (4.16 +/- 0.34 m/sec) and left (4.08 +/- 0.34 m/sec) sides in badminton players, and the control group exhibited same tendency (right: 4.36 +/- 0.25 m/sec, left: 4.28 +/- 0.33 m/sec) as well. These results suggest no training-induced change in the muscle fiber conduction velocity.     

Patterns of center of presure migration during prolonged unconstrained standing

Prolonged (>30 min) unconstrained standing (PUS) was studied in 10 young healthy subjects. The usual methods of stabilographic analysis assume a random center of pressure (COP) migration. This study was based on the opposite idea and showed that during PUS, specific and consistent patterns of the COP migration can be recognized by a computer algorithm. Three COP migration patterns were found: (a) shifting, a fast displacement of the average position of COP from one region to another; (b) fidgeting, a fast and large displacement and returning of COP to approximately the same position; and (c) drifting, a slow continuous displacement of the average position of COP. A software code was written and default parameter values were chosen for recognizing COP migration patterns. For 30-min PUS the following patterns were identified: Shifting was generally observed every 316 +/- 292 sec in the anterior-posterior (a-p) direction with an average shift amplitude of 17 +/- 15 mm, and every 199 +/- 148 sec in the medial-lateral (m-l) direction with an average shift amplitude of 22 +/- 38 mm. Corresponding time intervals for fidgeting were 59 +/- 15 sec in the a-p direction and 49 +/- 16 sec in the m-l direction. The average drift-to-drift interval was 319 +/- 173 sec in the a-p direction and 529 +/- 333 sec in the m-l direction.     

Neuromuscular blockade with vecuronium and its reversal with edrophonium during total intravenous anesthesia, neuroleptanalgesia and sevoflurane anesthesia

The neuromuscular blocking effect of vecuronium and its reversibility ith edrophonium were studied under total intravenous anesthesia (TIVA) and compared with those under NLA or sevoflurane anesthesia (SA) in 30 surgical patients. The degree of neuromuscular blockade was evaluated by acceleration of thumb adduction in response to supramaximal stimulation of the ulnar nerve using Accelograph (Biometer). TIVA was induced with droperidol 0.25 mg.kg-1, fentanyl 2-4 micrograms.kg-1 and ketamine 2 mg.kg-1, and maintained with continuous infusion of ketamine 2 mg.kg-1.h-1 with 30-35% O2 in air. NLA was induced with droperidol 0.25 mg.kg-1 and fentanyl 5-10 micrograms.kg-1 and maintained with 66% nitrous oxide in oxygen. SA was induced with thiamylal 5 mg.kg-1 i.v. and maintained with 66% nitrous oxide in oxygen supplemented with sevoflurane (1 MAC). A single bolus intravenous injection of vecuronium 0.1 mg.kg-1 was used for paralysis and reversed with edrophonium 0.75 mg.kg-1 followed by atropine 0.015 mg.kg-1 when the TOF ratio returned to 25%. The times required from administration of vecuronium to completion of maximal block with TIVA, NLA and SA were 196.5 +/- 52.2 sec, 182.5 +/- 47.6 sec and 166.0 +/- 69.0 sec, respectively. There was no significant difference among them. The times from completion of maximal block to 25% recovery of the twitch height in TIVA and NLA were 39.5 +/- 11.0 min and 37.4 +/- 5.8 min without significant difference. Those values, however, were significantly shorter than 64.5 +/- 35.2 min of SA.(ABSTRACT TRUNCATED AT 250 WORDS)     

New nortriterpenoid isolated from anti-rheumatoid arthritic plant, Tripterygium wilfordii, modulates tumor growth and neovascularization

Noninvasive measurement of blood flow velocity through the cardiac valves has important clinical applications. A wide variety of MR methods are available for flow measurement. The aim of this study was to investigate the ability of cine MR Fourier velocimetry to measure flow through healthy cardiac valves and to compare MR and Doppler peak velocity measurements. Ten healthy volunteers (age mean +/- SD, 24 +/- 4 years) without history of valvular disease were studied. Four of the subjects were females. In each subject, aortic, pulmonary, mitral, and tricuspid valves were evaluated with MR and Doppler imaging. A whole-body mobile MR machine was used, operating at .5-T with actively shielded magnetic field gradient coils on all three axes capable of 20 mT/m at a slew rate of 60 mT/ m/msec. The heart rate during MR and Doppler studies was not significantly different. The mean difference between the two studies was 2 beats/min, with a 95% confidence interval of -22 beats/min, +25 beats/ min. Peak systolic flow velocity in the aortic and pulmonary valves and peak diastolic flow velocity in the mitral and tricuspid valves measured with MRI and Doppler echocardiography correlated well. The mean difference between the two measurements (MR-Doppler) was 63 mm/sec, with a 95% confidence interval of -180 mm/sec, +310 mm/sec. The agreement between two observers interpreting the same MR velocity maps was close. The mean difference between their two measurements was 23 mm/sec, with a 95% confidence interval of -20 mm/sec, +60 mm/sec. There was no significant difference between MR and Doppler imaging or between the two MR observers. MR Fourier velocimetry has the necessary ease, reliability, and speed to measure blood flow through the cardiac valves, although measurement of late diastolic flow in the atrioventricular valves is limited. Measurement of peak blood velocity through the cardiac valves by this method showed satisfactory agreement with Doppler, but its clinical application for assessing diseased cardiac valves must be established.     

The importance of the Doppler angle

We examined 118 infrainguinal grafts (103 patients) to determine the effect changes in the angle of theta or Doppler angle had on the accuracy of velocity measurements made with a duplex scanner. Four separate measurements of peak velocity were made on each graft. Three measurements were made with the flow toward the probe at 60 degrees, 50 degrees, 120 degrees (60 degrees the other way). The probe was then turned 180 degrees so the flow was away from the probe and measurements were made at 60 degrees. When the primary cursor was aligned with the vessel wall (Technologist A), the mean velocity at 60 degrees was 69.4 cm/sec and 57.3 cm/sec at 50 degrees, a difference of 12 cm/sec. The same measurements done by Technologist B (primary cursor non aligned with the wall), showed a 10 cm/sec difference (60.7 and 50.5). We saw a consistent difference with even this small difference in the angle of theta throughout the study. The mean velocity obtained by Technologist A when the flow was toward the probe was 61.7. When the probe was turned 180 degrees (flow away from the probe), the mean velocity was 60.5. The same measurements by Technologist B were 51.8 and 50.5. This indicates that the direction of the flow of blood towards or away from the probe does not effect the velocity measurements. Using the vessel wall to line up the primary cursor provides a consistent and easily reproducible reference point to compare measurements made on different days but is less important for single measurements.     

F-wave velocity in motor neurone disease

The F-wave velocity in the central segment (axilla to spinal cord) was studied employing the "collison technique" described by Kimura (1974), and compared with the conduction velocity obtained with the usual methods. In 25 normal subjects the F-wave velocity increased proceeding proximally, reaching the maximum values in the central tract (64.86 +/- 2.23 m/sec in ulnar nerve). In 11 patients affected by motor neurone disease and 11 patients affected by amyotrophic lateral sclerosis the F-wave velocity decreased significantly proceeding proximally and the minimum values were found in the central tract (52.51 +/- 2.15 m/sec in MND and 48.64 +/- 5.60 m/sec in ALS). We therefore suggest the use of F-wave velocity as a more complete element for precise localization of the lesion in the central segment when the motoneurone is primarily involved.     

Tribological Properties of Hard Alloys Based on Chromium Carbide

Hard alloys of the type KKhN and KKhNF were studied and shown to have low coefficient of friction (f = 0.21-0.17) and wear rate (I = 5.7-7.0 m/km) at sliding velocity 15 m/sec and load 7 MPa, which make them promising for use as antifrictional materials in dry friction units under load. Oxide films formed at the surface of the hard alloys play the role of solid lubricants and decrease frictional losses.     

An experimental model of pleural cancer. Value of orthotopic implantation of human tumor tissue in nude mice

In a comparison article we report that maternal PO exposure to 2.5 mg/kg all-trans retinoic acid (RA) daily for 3 consecutive days over gestational days (GD) 11-13 produces a 10% reduction in weight of cerebellum at 4 weeks of age, not accompanied by other malformations. Here we report the results of a preliminary behavioral analysis of offspring exposed gestationally to RA as above. Exposed dams were allowed to deliver normally, and litters were culled to eight pups (4 +/- 1 of each sex) at birth. Both male and female offspring were tested prior to weaning on GD 21. Thereafter females were killed on postnatal day (PND) 28 for verification of RA effects on regional brain weight, and all subsequent behavioral testing was conducted on males. Preweaning tests were restricted to negative geotaxis (PND 8-9) and open field activity (PND 22). Postweaning tests included open field activity (PND 43), auditory startle response (three times, on PNDs 22, 43, and 84), 2-week activity in residential running wheels (PNDs 62-76), complex maze performance for 5 consecutive days (PND 83-87), emergence latency (PND 106), and assessment of the behavioral response to an amphetamine challenge (PND 107). Males were then killed on PND 108 for verification of RA effects on regional brain weights. In this study, RA reduced weight of cerebellum but not striatum. Cerebellar weight was 92% of control values in PND 28 females, and this weight difference had diminished to 95% of control weight by PND 108 in males. There were no treatment effects on negative geotaxis, activity in a small open field, auditory startle amplitude, or latency to enter an illuminated alley from a dark chamber. Maze learning occurred at levels equal to or slightly better than controls. Running wheel activity was enhanced by RA exposure, whereas activity in response to an amphetamine challenge was reduced by such exposure. We conclude that RA doses low enough to produce mild weight reductions in cerebellum, without attendant malformations, can alter behavior. The precise nature of these alterations remains to be elucidated, but the findings reported here suggest that effects may be more pronounced on activity than on learning.     

Scintillation splenoportography: hemodynamic and morphological study of the portal circulation

The intrasplenic injection of 99mTc-labeled albumin microspheres, followed 30 sec later by an injection of 99mTc-labeled red blood cells with recording of the progression of the two tracers, were performed in 110 patients. This also enabled the plotting of activity versus time curves on splenic, hepatic, cardiac, and pulmonary areas of interest, there by giving access to several hemodynamic variables. Scintillation image demonstrated splenoportal obstruction in 8 cases. Intrahepatic obstruction with reflux via collaterals were observed in 53 cases, 14 with umbilical reflux. In 13 cases, the patency of surgical portacaval anastomoses were verified. The splenoportal blood flow velocity was not significantly different in patients with cirrhosis (V = 10.1 cm per sec +/- 3.0 SD) and in normal subjects (V = 13.2 cm per sec +/- 5.8 SD). The fraction of shunted splenic flow in the case of cirrhosis varied from 0 to 100%; there was no relationship between this percentage and the seriousness of the clinical status. In 3 cases, the presence of intrahepatic shunts was detected. There was a very significant difference between mean transit time (MTT) of red blood cells in patients with cirrhosis (t = 12.2 sec +/- 4.4 SD) and those without cirrhosis (t = 19.9 sec +/- 3.7 SD). Among patients with cirrhosis, those with a history of jaundice had a shorter MTT than those without such a history. On the other hand, the MTT was not significantly different whether the patients with cirrhosis had or did not have hemorrhage, ascites or encephalopathy. There was a positive correlation (P less than 0.01) between MTT and plasma albumin concentration,and between MTT and prothrombin (P less than 0.01). Finally, there was a high negative correlation (P less than 0.001) between MTT and total serum bilirubin. Scintillation splenoportography is a useful technique for assessing hepatic hemodynamics and for demonstrating abnormalities of the intrahepatic circulation.     

Reticulospinal systems mediate atonia with short and long latencies

The pontomedullary region is responsible for both the tonic and phasic reduction of muscle activity in rapid-eye-movement sleep and contributes to the control of muscle tone in waking. This study focused on determining the time course of activity in the pontomedullary systems mediating atonia. Short-train stimulations (3 0.2-ms pulses at 330 Hz) of the pons and medulla suppressed neck and hindlimb muscle activity in decerebrate cats. We identified two distinct phases of suppression, early and late. The anatomic sites that produced each suppression were intermixed. We estimated the dividing value of the conduction velocity for reticulospinal projections responsible for early and late phases of hindlimb muscle tone suppression to be 22.8 m/s. In the medial medulla, 238 reticulospinal units, which send axons to the L1 level of the spinal cord, were identified. Pontine stimulation that suppressed hindlimb muscle tone increased the firing rate of 138 units (type I). Sixteen type I units showed a delayed response to the pontine stimulation with a latency of 10 ms or longer (type Id), whereas 122 type I units exhibited an earlier response (type Ie). Seven type Ie units had an axonal conduction velocity of <22.8 m/s, whereas the remaining 115 conducted at faster than 22.8 m/s. Early and late hindlimb muscle tone suppressions were hypothesized to be mediated through fast and slow conducting type Ie reticulospinal units. The activity of type Id neurons may contribute to the cessation of the early-phase suppression as well as to the induction, maintenance, or cessation of the late-phase suppression.     

Microsatellite variation in the Australian dingo

Shoulder arthroplasty (SA) is commonly performed in patients with rheumatoid arthritis (RA) who have been treated with long-term immunosuppressive medication. RA is associated with an increased risk of neoplasms of the immune system. A case of non-Hodgkin's lymphoma as an unexpected diagnosis after the routine pathologic examination of the soft tissues after SA was detected in a 54-year-old woman with long-standing RA and prolonged immunosuppressive therapy. Although this case does not support the cost-effectiveness of routine specimen evaluation during SA, we suggest that histological analysis of the surgical tissues is appropriate and should be performed in all patients who have been treated with prolonged immunosuppressive medication, especially RA patients as well as patients who have suspicious surgical findings.