Control strategies in directing the hand to moving targets

We have evaluated the use of visual information about the movement of a target in two tasks--tracking and interceptions--involving multi-joint reaching movements with the arm. Target velocity was either varied in a pseudorandom order (random condition) or was kept constant (predictable condition) across trials. Response latency decreased as target velocity increased in each condition. A simple model that assumes that latency is the sum of two components--the time taken for target motion to be detected, and a fixed processing time--provides a good fit to the data. Results from a step-ramp experiment, in which the target stepped a small distance immediately preceding the onset of the ramp motion, were consistent with this model. The characteristics of the first 100 ms of the response depended on the amount of information about target motion available to the subject. In the tracking task with randomly varied target velocities, the initial changes in hand velocity were largely independent of target velocity. In contrast, when the velocity was predictable the initial hand velocity depended on target velocity. Analogously, the initial changes in the direction of hand motion in the interception task were independent of target velocity in the random condition, but depended on target velocity in the predictable condition. The time course for development of response dependence was estimated by controlling the amount of visual information about target velocity available to the subject before the onset of limb movement. The results suggest that when target velocity was random, hand movement started before visual motion processing was complete. The response was subsequently adjusted after target velocity was computed. Subjects displayed idiosyncratic strategies during the catch-up phase in the tracking task. The peak hand velocity depended on target velocity and was similar for all subjects. The time at which the peak occurred, in contrast, varied substantially among subjects. In the interception task the hand paths were straighter in the predictable than in the random condition. This appeared to be the result of making adjustments in movement direction in the former condition to correct for initially inappropriate responses.

Fibrosing cytolytic liver failure secondary to recurrent hepatitis B after liver transplantation

Four patients who underwent transplantation for hepatitis B virus-related liver disease developed rapidly progressive liver failure attributable to recurrent hepatitis B disease typified by hyperbilirubinemia and distinctive hepatocyte ballooning and progressive fibrosis consistent with recently reported fibrosing cholestatic hepatitis. Among these four patients, the mean interval from transplantation to redocumentation of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) was 5 months, to development of malaise and jaundice 6 months, to histological diagnosis 7 months, and to graft failure 8 months. The only patient who underwent retransplantation had accelerated recurrence of the same syndrome with biopsy documentation 1 month later and graft failure 2 months later. Distinctive histological features included confluent hepatocellular ballooning and progressive periportal fibrosis followed by lobular collapse over 4-6 weeks without significant inflammation. Immunohistochemical staining showed marked HBsAg and hepatitis B core antigen (HBcAg) immunoreactivity. The rapid development of cytolytic hepatocellular necrosis and lobular collapse with prominent HBcAg immunoreactivity without significant inflammation suggests a cytolytic rather than immune pathogenesis for this unique and devastating form of recurrent hepatitis B that might better be termed "fibrosing cytolytic hepatitis."

Parkinson's disease and exposure to agricultural work and pesticide chemicals

This population-based case-control study of 130 Calgary residents with neurologist-confirmed idiopathic Parkinson's disease (PD) and 260 randomly selected age- and sex-matched community controls attempted to determine whether agricultural work or the occupational use of pesticide chemicals is associated with an increased risk for PD. We obtained by personal interviews lifetime occupational histories, including chemical exposure data, and analyzed the data using conditional logistic regression for matched sets. In the univariate analysis, a history of field crop farming, grain farming, herbicide use, or insecticide use resulted in a significantly increased crude estimate of the PD risk, and the data suggested a dose-response relation between the PD risk and the cumulative lifetime exposure to field crop farming and to grain farming. However, in the multivariate analysis, which controlled for potential confounding or interaction between the exposure variables, previous occupational herbicide use was consistently the only significant predictor of PD risk. These results support the hypothesis that the occupational use of herbicides is associated with an increased risk for PD.

23Na- and 31P-NMR studies of perfused mouse liver during nitrogen hypoxia

The effects of nitrogen hypoxia on isolated perfused mouse livers from fed mice were studied at 37 degrees C using 23Na and 31P nuclear magnetic resonance (NMR) spectroscopy. The paramagnetic shift reagent, dysprosium-triethylenetetraminehexaacetic acid, was used to distinguish intracellular from extracellular sodium. The area of the intracellular sodium resonance remained relatively constant over the first 30 min of hypoxia and then increased by a factor of approximately 2 relative to controls over the next 30 min. High-energy phosphate metabolites were measured using 31P-NMR. The beta-ATP resonance decreased to zero, and the intracellular pH decreased from 7.3 to 6.9 during 60 min of hypoxia. Liver enzyme activity in the effluent exiting the liver increased in direct proportion to the length of hypoxia up to 56 min. The sodium, ATP, and enzyme changes during hypoxia were correlated with histological and electron-microscopic findings. The morphology of liver specimens exposed to 30 min of hypoxia was close to normal, whereas extensive centrilobular and midlobular necrosis was seen in specimens subjected to 60 and 90 min of hypoxia. The effect of 30 min of reoxygenation after 15, 30, 45, 60, and 90 min of hypoxia was also studied. The level of beta-ATP recovery depended on the duration of hypoxia. For 60 min of hypoxia followed by reoxygenation, beta-ATP recovered to only 20% of control values. The morphology of hypoxic livers after 30 min of reoxygenation was similar to livers subjected to hypoxia alone.

Transjugular liver biopsy

Although transjugular liver biopsy requires the availability of trained personnel, takes more time than percutaneous biopsy and is moderately expensive, it is a safe alternative technique for obtaining adequate liver tissue for diagnosis in special clinical situations. The usual indications for transjugular rather than percutaneous liver biopsy are (a) coagulation disorder (prothrombin time greater than 3 sec over control value and/or platelet count less than 60,000/cm3), (b) massive ascites and (c) desire to perform ancillary procedures, such as measurement of pressures or opacification of the hepatic veins and inferior vena cava. Less common indications for transjugular liver biopsy include failed percutaneous biopsy, massive obesity, small cirrhotic liver (increased risk and lower success rate) and suspected vascular tumor or peliosis hepatis. Results from several centers indicate that adequate or diagnostic liver tissue is obtained in 81% to 97% of cases. The typical length of the biopsy core ranges from 0.3 cm to 2.0 cm. Modification of the classic technique, particularly the adaptation of a Tru-Cut needle, shows promise in yielding longer cores of tissue with less fragmentation. Transjugular liver biopsy is performed with an acceptable complication rate that ranges 0% to 20%. The reported mortality of transjugular liver biopsy was 0 in three major centers and ranged from 0.1% to 0.5% in three other centers. Transjugular liver biopsy may be useful in obtaining diagnostic liver tissue not only in advanced chronic liver disease with coagulopathy, ascites or both, but also in patients with fulminant hepatic failure to better determine prognosis and the need for liver transplantation.

Multi-joint reaching movements and eye-hand tracking in cerebellar incoordination: investigation of a patient with complete loss of Purkinje cells

Performance on an eye-hand tracking task and a multi-joint reaching movement to a visual target was studied in a patient with stable cerebellar ataxia and in control subjects. The patient subsequently died and a full neuropathological examination was performed. The neuropathological findings were similar to those seen in patients with paraneoplastic cerebellar degeneration, but no tumor was found at autopsy eight years after onset of the patient's cerebellar syndrome. A severe cerebellar cortical degeneration with complete Purkinje cell loss was demonstrated, whereas cerebellar nuclei and brainstem structures showed no neuronal loss. Tracking performance by the patient was characterized by abnormally large numbers of high velocity movements and hand direction reversals, and by excessive lagging of the hand behind the target in time. In the multi-joint reaching movement, the patient showed a delay in movement onset at the elbow joint compared to movement onset at the shoulder joint. The velocity profile of the movement at the shoulder joint was abnormal. The duration of the acceleration phase was poorly correlated with both peak angular velocity and the duration of the deceleration phase. One of the most striking findings was the inability of the patient to consistently produce the same movement direction from trial to trial while reaching to the same target. Our data suggests that the cerebellar cortex is involved in multiple aspects of motor control including visuomotor integration mechanisms.

Giardia and Cryptosporidium spp. in filtered drinking water supplies

Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for filtered drinking water samples collected from 66 surface water treatment plants in 14 states and 1 Canadian province. Giardia cysts were detected in 17% of the 83 filtered water effluents. Cryptosporidium oocysts, were observed in 27% of the drinking water samples. Overall, cysts or oocysts were found in 39% of the treated effluent samples. Despite the frequent detection of parasites in drinking water, microscopic observations of the cysts and oocysts suggested that most of the organisms were nonviable. Compliance with the filtration criteria outlined by the Surface Water Treatment Rule of the U.S. Environmental Protection Agency did not ensure that treated water was free of cysts and oocysts. The average plant effluent turbidity for sites which were parasite positive was 0.19 nephelometric turbidity units. Of sites that were positive for Giardia or Cryptosporidium spp., 78% would have been able to meet the turbidity regulations of the Surface Water Temperature Rule. Evaluation of the data by using a risk assessment model developed for Giardia spp. showed that 24% of the utilities examined would not meet a 1/10,000 annual risk of Giardia infection. For cold water conditions (0.5 degree C), 46% of the plants would not achieve the 1/10,000 risk level.

Occurrence of Giardia and Cryptosporidium spp. in surface water supplies

Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for source waters of 66 surface water treatment plants in 14 states and 1 Canadian province. The results showed that cysts and oocysts were widely dispersed in the aquatic environment. Giardia spp. were detected in 81% of the raw water samples. Cryptosporidium spp. were found in 87% of the raw water locations. Overall, Giardia or Cryptosporidium spp. were detected in 97% of the raw water samples. Higher cyst and oocyst densities were associated with source waters receiving industrial or sewage effluents. Significant correlations were found between Giardia and Cryptosporidium densities and raw water quality parameters such as turbidity and total and fecal coliform levels. Statistical modeling suggests that cyst and oocyst densities could be predicted on the basis of watershed and water quality characteristics. The occurrence of high levels of Giardia cysts in raw water samples may require water utilities to apply treatment beyond that outlined in the Surface Water Treatment Rule of the U.S. Environmental Protection Agency.

Parkinson's disease and exposure to rural environmental factors: a population based case-control study

To determine whether a history of exposure to rural environmental factors leads to an increased likelihood of developing idiopathic Parkinson's disease, we conducted a case-control study of 130 cases and 260 randomly selected community controls (matched with the cases by sex and age +/- 2.5 years at a ratio of 2 controls: 1 case) in the city of Calgary. The data were collected by personal interviews and were analyzed using conditional logistic regression for matched sets. The ages of the cases ranged from 36.5 to 90.7 years (mean = 68.5 +/- 11.3 years). The mean age at diagnosis was 61.1 +/- 12.4 years. The mean duration of disease was 7.8 +/- 0.6 years. Eleven (9.1%) cases were diagnosed before age 40. In this sample from the Province of Alberta, Canada, no significant increase in risk for Parkinson's disease was associated with a history of rural living, farm living, or well water drinking in early childhood or at any time during the first 45 years of life.

Reciprocal Ia inhibition in patients with spinal spasticity

Reciprocal Ia inhibition from ankle flexors to extensors was studied in five patients with spasticity due to incomplete traumatic spinal cord lesions. Nine healthy subjects were tested as controls. Excitability of the soleus motoneuron pool was estimated by H-reflex testing in the resting state. Ia inhibition was activated by conditioning stimuli to the peroneal nerve. Ia inhibition was detected in all patients tested, the amount of inhibition ranging from 8% to more than 50% of the test H-reflex size. In the control subjects only weak Ia inhibitory effects were present. These findings indicate increased excitability of the Ia inhibitory pathway to ankle extensor motoneurons in patients with spasticity due to spinal cord injury.

Verapamil improves rat hepatic preservation with UW solution

Verapamil, a calcium channel blocker, improves myocardial preservation during cold cardioplegia and protects against renal damage during periods of warm and cold ischemia. To determine if verapamil could prevent ischemic damage to livers during and after cold storage, harvested rat livers were flushed with either University of Wisconsin (UW) solution or UW solution with 25 mg/liter verapamil. Twenty rats were used in each group. After 24 hr of storage at 4 degrees C, livers were perfused with oxygenated blood through the portal veins for 2 hr at 37 degrees C and pH 7.4. Liver enzymes, electrolytes, and perfusate flow rate were determined at 30-min intervals. At 90 min of perfusion, the verapamil group of livers had less elevation of AST (110 +/- 17 IU/liter vs 172 +/- 25 IU/liter, P less than 0.05), ALT (115 +/- 21 IU/liter vs 210 +/- 34 IU/liter, P less than 0.05), and LDH (962 +/- 170 IU/liter vs 1452 +/- 253 IU/liter, NS). Verapamil livers produced more bile than controls (6.9 +/- 1.9 microliters/g vs 2.3 +/- 1.7 microliter/g, P less than 0.05) and maintained a higher portal flow rate throughout the perfusion. Both groups showed similar reduction in liver weights after storage (3.9 +/- 0.9% vs 2.8 +/- 0.7%) and required the same amount of bicarbonate for correction of acidosis during perfusion (2.6 +/- 0.2 mM vs 2.8 +/- 0.2 mM). Light microscopic exam after perfusion showed hepatocyte damage in 30% of control livers, but 0% of verapamil livers. We conclude that verapamil-treated rat livers showed less damage and better function upon reperfusion after 24 hr of cold storage. This agent may be clinically useful as an additive to the UW preservation solution for livers.

Initial two-year results of the Oregon Liver Transplantation Program

During the first 24 months of the Oregon Liver Transplantation Program, which began in October 1988, 94 patients were formally evaluated and 47 adults underwent 54 liver transplantations. Thirty-four percent of patients were veterans. The recipient operation lasted a mean of 7.4 hours (range: 4 to 16 hours). Veno-venous bypass was used routinely at first but selectively later (7 of the last 26 cases), resulting in reduced operating time. Hepatic artery reconstruction was end-to-end anastomosis in 52 cases and iliac conduit in 2. No arterial thrombosis occurred. Biliary reconstruction was choledochocholedochostomy in 83% and choledochojejunostomy in 17%. Biliary complications occurred in 28%. Operative mortality was 2%, and 1-year actual survival was 80%. Patients with hepatitis B fared worse, with four of six dying at a mean of 7.6 months. Overall, the median hospital stay was 30 days. Patients surviving more than 3 months had a mean Karnofsky score of 82%. No significant difference in outcome was noted in patients receiving prophylactic OKT3 monoclonal antibody (used in 45%) versus conventional immunosuppressive therapy. Overall, allograft rejection occurred in 55% of patients. Retransplantation was required in seven patients, three for primary graft nonfunction, two for uncontrolled rejection during induction therapy with OKT3, and two for graft failure secondary to recurrent hepatitis B.

Bacterial nutrients in drinking water

Regrowth of coliform bacteria in distribution systems has been a problem for a number of water utilities. Efforts to solve the regrowth problem have not been totally successful. The current project, which was conducted at the New Jersey American Water Co.-Swimming River Treatment Plant, showed that the occurrence of coliform bacteria in the distribution system could be associated with rainfall, water temperatures greater than 15 degrees C, total organic carbon levels greater than 2.4 mg/liter, and assimilable organic carbon levels greater than 50 micrograms of acetate carbon equivalents per liter. A multiple linear regression model based on free chlorine residuals present in dead-end sections of the distribution system and temperature predicted 83.8% of the heterotrophic plate count bacterial variation. To limit the growth of coliform bacteria in drinking water, the study concludes that assimilable organic carbon levels should be reduced to less than 50 micrograms/liter.

Manual tracking performance in patients with cerebellar incoordination: effects of mechanical loading

Manual tracking performance was studied in five patients with cerebellar incoordination due to unilateral cerebellar hemisphere lesions. The subjects were required to track a target on an oscilloscope screen by moving a cursor controlled by flexion-extension movements of the wrist. In comparison to normal subjects, the cerebellar patients, using their clinically affected arm, demonstrated irregular tracking patterns with inappropriate accelerations and decelerations, numerous high velocity peaks of movement, and an increased time lag between the cursor and the target. The addition of a viscous load provided by feeding back wrist velocity to a torque motor coupled to the apparatus resulted in significant improvement in tracking performance and suppression of the high velocity peaks. Increasing elastic stiffness by feeding back wrist position or inertial load by adding weights to the hand did not improve performance on this task. It is proposed that a hypotonic cerebellar limb behaves like an underdamped mechanical system. The addition of viscous loads helps restore more normal damping during voluntary movements of the arm.

Effects of unexpected perturbations on trajectories and EMG patterns of rapid wrist flexion movements in humans

To investigate how motor programs can be modified by sensory inputs we recorded kinematic and EMG patterns from normal human subjects performing well-practised wrist flexion movements in response to an auditory tone. On random trials unexpected wrist perturbations were introduced at varying times after the signal to move had been given. Extension perturbations delivered before agonist EMG onset resulted in an increased maximum velocity (MV) during the wrist flexion movement and in an increased target overshoot even though the wrist was further from the target than expected by the subject at the onset of the movement. The first agonist EMG burst and the antagonist burst were both increased in magnitude in these perturbed trials. Flexion perturbations delivered before the agonist EMG onset moved the hand nearer to the target just prior to movement onset. These resulted in a reduced MV, but the expected increased target overshoot did not occur. The first agonist burst was reduced in magnitude, and the antagonist burst was increased in magnitude. Perturbations delivered after agonist EMG onset produced less change in the first agonist and antagonist EMG burst, and less compensation for the perturbation was evident in wrist position and velocity recordings. These results indicate that, at least in some situations, motor programs for rapid voluntary movements can be modified by afferent inputs. This interaction between central motor commands and sensory feedback might occur at the cortical or spinal level, depending on when perturbations occur relative to onset of EMG and movement. The timing of the EMG changes suggest that both reflex mechanisms and longer latency 'voluntary' adjustments contribute to the compensatory changes in movement trajectory.

Gastrointestinal involvement in Langerhans cell histiocytosis (histiocytosis X): diagnosis by rectal biopsy

We report two patients with biopsy-proven involvement of the gastrointestinal tract by Langerhans cell histiocytosis (LCH). The two patients were infants with congenital cutaneous lesions and bloody diarrhea beginning at 1 or 2 wk of age. Rectal biopsy specimens showed a mucosal infiltrate of typical Langerhans cells that focally invaded and destroyed the crypt epithelium. Gastrointestinal involvement by LCH is unusual and only rarely has represented a prominent clinical manifestation. In most cases, such involvement has been an indicator of widespread multisystemic disease. Its distinctive morphologic and immunohistochemical features allow LCH to be distinguished from other histiocytic infiltrations found in mucosal biopsy specimens.

The doctor's changing role in allocating U.S. and British medical services

Until the fourth decade of this century, British and American patients who could afford physician services paid for them out of their own pockets; those who could not relied on charity care or simply went without. Doctors functioned as independent contractor private practitioners in both Great Britain and the United States, allocating medical services in response to paying-patient demand — and their own consciences.

Beginning in the 1930s, health care financing on both sides of the Atlantic was restructured in dramatically different directions, and physicians’ allocational roles in their respective countries began diverging. Under the National Health Service (NHS), British general practitioners became essentially gatekeepers to health services, funneling patients to appropriate hospital and specialist care. As time went by they came more to resemble lockkeepers, regulating the queue for secondary and tertiary treatment resulting from governmental limits on health care spending — and from the limitations and inefficiencies of a system of rationing by waiting. In the U.S., on the other hand, efficiency was not at first a concern.

Sclerosing peritonitis

An unusual case of widespread peritoneal fibrosis of unknown cause ("sclerosing peritonitis") is described. The patient presented with ascites and bowel obstruction and was found to have numerous fibrous plaques involving primarily the serosa of the small bowel. The plaques were composed of bland spindle cells, ultrastructurally characterized as myofibroblasts, set within a collagenous stroma. Progressive involvement led to the patient's death 17 months after onset of symptoms. A literature review shows similar cases reported with a variety of names and a number of associated clinical conditions, none of which was present in this patient. The pathologic features seen in this case suggest that sclerosing peritonitis represents a nonspecific reaction of the peritoneal surface to a variety of insults and is characterized by florid reactive hyperplasia of submesothelial mesenchymal cells.

Anterior lesser curvature laser seromyotomy with posterior truncal vagotomy: a potential treatment of peptic ulcer disease

Anterior lesser curvature seromyotomy combined with posterior truncal vagotomy has been suggested as an alternative to proximal gastric vagotomy in the treatment of peptic ulcer. The argon laser may be an ideal instrument for performing seromyotomy. This study compares anterior lesser curvature argon laser seromyotomy/posterior or truncal vagotomy with anterior proximal gastric vagotomy/posterior truncal vagotomy in a canine preparation. Six dogs underwent anterior lesser curvature argon laser seromyotomy/posterior truncal vagotomy and six others underwent anterior proximal gastric vagotomy/posterior truncal vagotomy. Gastric emptying and acid secretion studies were performed preoperatively and at 1 and 6 months postoperatively. Operating time and blood loss were determined. Anterior lesser curvature argon laser seromyotomy was performed with the argon laser at 10 W, continuous, delivered through a 600 micron unsheathed quartz fibre. Anterior proximal gastric vagotomy and posterior truncal vagotomy were performed in the standard fashion. Solid phase gastric emptying was slowed with both operations (P less than 0.05) but this was not manifest clinically. Blood loss (millilitres) was less following anterior lesser curvature argon laser seromyotomy/posterior truncal vagotomy than following anterior proximal gastric vagotomy/posterior truncal vagotomy (21(6.8) versus 95(28.1), mean (s.e.m.), P less than 0.05) but operating time was not significantly different between the groups. Mean basal acid secretion was reduced by 64 per cent 6 months after anterior lesser, curvature argon laser seromyotomy/posterior truncal vagotomy (P less than 0.05) and by 53 per cent after anterior proximal gastric vagotomy/posterior truncal vagotomy (not significant). Mean stimulated acid secretion was reduced by 41 per cent 6 months after anterior lesser curvature argon laser seromyotomy/posterior truncal vagotomy (P less than 0.05) and by 24 per cent after anterior proximal gastric vagotomy/posterior truncal vagotomy (not significant). We conclude that anterior lesser curvature argon laser seromyotomy/posterior truncal vagotomy is an acceptable alternative to anterior proximal gastric vagotomy/posterior truncal vagotomy and may provide superior parietal cell denervation with less operative blood loss.

Nonalcoholic steatohepatitis: a study of 49 patients

Nonalcoholic steatohepatitis (NASH) refers to an alcoholic hepatitis-like histologic pattern found in nonalcoholic patients. A review of 543 liver biopsies diagnosed as alcoholic hepatitis yielded 49 cases of NASH. The patients were commonly middle-aged women who were obese and often diabetic. NASH was usually discovered because of abnormal liver function tests or hepatomegaly noted during evaluation of other medical problems. Histologic examination revealed the same spectrum of changes found in alcoholic hepatitis, including cirrhosis in eight patients. Follow-up information was available for 39 patients after an average length of 3.8 years. Only one patient developed hepatic decompensation or died with liver failure or portal hypertension. Repeat histologic material was available for 13 patients after a mean 3.5 years of follow-up. Five patients showed progression of fibrosis, with cirrhosis developing in two, but the other eight patients demonstrated little morphologic change. These findings indicate that NASH is, in general, a clinically mild and biologically low-grade condition, but with the potential to progress and evolve into cirrhosis in some patients. The factors promoting progression are unclear.

Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.