Dopamine lesions alter the striatal encoding of single-limb gait

The striatum serves an important role in motor control, and neurons in this area encode the body's initiation, cessation, and speed of locomotion. However, it remains unclear whether the same neurons also encode the step-by-step rhythmic motor patterns of individual limbs that characterize gait. By combining high-speed video tracking, electrophysiology, and optogenetic tagging, we found that a sizable population of both D1 and D2 receptor expressing medium spiny projection neurons (MSNs) were phase-locked to the gait cycle of individual limbs in mice. Healthy animals showed balanced limb phase-locking between D1 and D2 MSNs, while dopamine depletion led to stronger phase-locking in D2 MSNs. These findings indicate that striatal neurons represent gait on a single-limb and step basis, and suggest that elevated limb phase-locking of D2 MSNs may underlie some of the gait impairments associated with dopamine loss.

Dopamine lesions alter the striatal encoding of single-limb gait

The striatum serves an important role in motor control, and neurons in this area encode the body's initiation, cessation, and speed of locomotion. However, it remains unclear whether the same neurons also encode the step-by-step rhythmic motor patterns of individual limbs that characterize gait. By combining high-speed video tracking, electrophysiology, and optogenetic tagging, we found that a sizable population of both D1 and D2 receptor expressing medium spiny projection neurons (MSNs) were phase-locked to the gait cycle of individual limbs in mice. Healthy animals showed balanced limb phase-locking between D1 and D2 MSNs, while dopamine depletion led to stronger phase-locking in D2 MSNs. These findings indicate that striatal neurons represent gait on a single-limb and step basis, and suggest that elevated limb phase-locking of D2 MSNs may underlie some of the gait impairments associated with dopamine loss.

Severe acute respiratory syndrome (SARS): epidemiology and clinical features

Severe acute respiratory syndrome (SARS) is a newly emerged infectious disease with a significant morbidity and mortality. The major clinical features include persistent fever, chills/rigor, myalgia, malaise, dry cough, headache, and dyspnoea. Older subjects may present without the typical febrile response. Common laboratory features include lymphopenia, thrombocytopenia, raised alanine transaminases, lactate dehydrogenase, and creatine kinase. The constellation of compatible clinical and laboratory findings, together with certain characteristic radiological features and lack of clinical response to broad spectrum antibiotics, should arouse suspicion of SARS. Measurement of serum RNA by real time reverse transcriptase-polymerase chain reaction technique has a detection rate of 75%-80% in the first week of the illness.

Clinical course of peritonitis due to Pseudomonas species complicating peritoneal dialysis: a review of 104 cases

BACKGROUND

Peritonitis due to Pseudomonas species is a serious complication in continuous ambulatory peritoneal dialysis (CAPD) patients. The clinical course of peritonitis due to Pseudomonas complicating CAPD remains unclear.

METHODS

All of the Pseudomonas species episodes of peritonitis in our dialysis unit were studied from 1995 to 1999. During this period, there were 859 episodes of peritonitis recorded, 113 of which were caused by the Pseudomonas species. Nine episodes were excluded because they were mixed growth. The remaining 104 episodes in 68 patients were reviewed.

RESULTS

The underlying renal diagnosis and prevalence of comorbid conditions of the 68 patients were similar to those found in our entire dialysis population. There was a history of antibiotic therapy within 30 days of the onset of peritonitis due to the Pseudomonas species in 69 episodes (66.3%). In 47 episodes (45.2%) there was a concomitant exit site infection. The overall primary response rate was 60.6% and the complete cure rate was 22.1%. The presence of exit site infection was associated with a lower primary response rate (22 in 47 vs. 41 in 57 episodes, P < 0.01) and a lower complete cure rate (5 in 47 vs. 18 in 57 episodes, P < 0.02). The episodes that had received recent antibiotic therapy had a significantly lower complete cure rate than the de novo cases (8 in 69 vs. 15 in 35 episodes, P < 0.001). Episodes receiving third-generation cephalosporin as part of the initial antibiotic regimen had a significantly higher primary response rate than the ones that initially received aminoglycoside (54 in 81 episodes vs. 8 in 22 episodes, P < 0.05), but their complete cure rates were similar. Twenty-four cases failed to respond to antibiotics and the Tenckhoff catheter was removed. The chance of returning to CAPD was higher when the Tenckhoff catheter was removed on day 10 than on day 15 (9 in 14 cases vs. 5 in 10 cases), although the result was not statistically significant. The Tenckhoff catheter was removed and replaced at another site simultaneously in another 14 cases after the effluent cleared up. None of these patients had a relapse of peritonitis within three months.

CONCLUSIONS

Recent antibiotic therapy is the major risk factor for peritonitis due to the Pseudomonas species. Exit site infection and recent antibiotic therapy are associated with poor therapeutic response to antibiotics. When the therapeutic response is suboptimal, early Tenckhoff catheter removal may help preserve the peritoneum for further peritoneal dialysis. Elective Tenckhoff catheter exchange after clearing up the peritoneal dialysis effluent may also reduce the likelihood of relapse. It is desirable to use third-generation cephalosporin in the initial antibiotic regimen for peritonitis treatment in localities with a high incidence of peritonitis due to the Pseudomonas species.

The role of lean body mass as a nutritional index in Chinese peritoneal dialysis patients--comparison of creatinine kinetics method and anthropometric method

OBJECTIVE

To compare, in Chinese continuous ambulatory peritoneal dialysis (CAPD) patients, the creatinine kinetics method (LBM-CK) and the anthropometric method (LBM-AM) for determining lean body mass (LBM).

DESIGN

Single-center cross-sectional study.

PATIENTS AND METHODS

We studied 151 unselected CAPD patients (78 males, 73 females). We calculated LBM-CK and LBM-AM using standard formulas. The results of the two methods were then compared by the Bland and Altman method. Dialysis adequacy and other nutritional indices, including total Kt/V, weekly creatinine clearance (CCr), residual glomerular filtration rate (GFR), protein nitrogen appearance (PNA), subjective global assessment (SGA), and serum albumin, were measured simultaneously.

RESULTS

The mean age of the patients was 55.6 +/- 12.2 years, and the mean duration of dialysis was 33.6 +/- 28.5 months. The mean body mass index (BMI) was 22.7 +/- 3.7. The average LBM-AM was 43.6 +/- 8.0 kg; the average LBM-CK was 33.0 +/- 9.3 kg. The difference between the calculated LBM-AM and LBM-CK was 10.7 kg, with LBM-AM always giving a higher value; the limits of agreement were -5.8 kg and 27.1 kg. The difference between the two measures correlated with residual GFR (Pearson r = 0.629, p < 0.001). After normalizing for desired body weight, LBM-AM was only modestly correlated with serum albumin level. No correlations were found between overall SGA score or normalized protein nitrogen appearance (nPNA) and LBM-AM or LBM-CK.

CONCLUSIONS

In Chinese patients at least, a substantial discrepancy exists between LBM-AM and LBM-CK. The difference is especially marked in patients with significant residual renal function. The optimal method for determining LBM remains obscure in Chinese CAPD patients. Moreover, LBM correlated poorly with other nutritional indices. Multiple parameters should be taken into consideration in an assessment of nutritional status of CAPD patients.