Biomedical subjects

P Silverstein

Publications and source records attributed to P Silverstein.

At least 19 recordsLinked to original sources

PubMed1994

Acute effects of levodopa on wrist movement in Parkinson's disease. Kinematics, volitional EMG modulation and reflex amplitude modulation.

Acute changes in motor performance due to levodopa were evaluated by a series of four motor tests unified by their focus on wrist flexion-extension movements. Subjects with idiopathic Parkinson's disease were evaluated with this battery of tests before (OFF) and after their usual morning dose of levodopa (ON). The test battery consisted of (i) repetitive self-paced movement in which velocity was to be maximized; (ii) visually guided tracking of a sinusoid and a square wave; and (iii) an assay of stretch reflex modulation during volitional sinusoidal tracking. The maximal wrist joint velocity of self-paced reciprocating flexion and extension movements increased after levodopa (ON), without significant changes in the movement period or amplitude. In the two tracking tasks, some subjects improved as evident by a lower root mean square (rms) error, but in similar numbers of subjects the rms error increased. Overall, the rms error, peak velocity or peak movement amplitude did not change after levodopa in either tracking task. Significant and consistent changes did occur after levodopa in an assay of reflex modulation during error-constrained tracking (Johnson et al., Brain 1991; 114: 443-60). The amplitude of volitional EMG increased after levodopa, with a concurrent reduction in reflex EMG. These changes are consistent with the noted increase in movement velocity. These results show that the effects of levodopa on movement velocity were not consistently translated into increased accuracy. The changes in the long latency reflex gain argue for a central control of this reflex, mediated by structures sensitive to levodopa. Finally, the results show that the quantitative evaluation of levodopa therapy cannot be unidimensional, but requires a battery of motor tests as undertaken in this study.

Aged↗

PubMed1993

Spatial updating in Parkinson's disease.

We compared the ability of 48 patients with Parkinson's disease (PD) (24 mild, 24 moderate) and 35 controls to remain oriented to the starting position after being transported passively in a wheelchair in two conditions: visual and vestibular. The moderate PD group demonstrated the poorest performance in both sensory conditions. The visual condition discriminated between the mild PD group and the controls, but both groups had similar performance in the vestibular condition. Poor performance of the PD group in the visual condition and controls in the vestibular condition correlated significantly with poor performance on selected balance tests. Poor performance in the visual condition correlated significantly with poor performance on judgment of line orientation in the mild PD group. Spatial updating, or maintaining a sense of orientation while being moved in the environment, may be impaired in PD and should be investigated as a possible contributing factor to problems with spatial orientation noted clinically in some patients.

Aged↗

PubMed1992

Smoking and wound healing.

The association between cigarette smoking and delayed wound healing is well recognized in clinical practice, although extensive controlled studies have yet to be performed. The documented effects of the toxic constituents of cigarette smoke--particularly nicotine, carbon monoxide, and hydrogen cyanide--suggest potential mechanisms by which smoking may undermine expeditious wound repair. Nicotine is a vasoconstrictor that reduces nutritional blood flow to the skin, resulting in tissue ischemia and impaired healing of injured tissue. Nicotine also increases platelet adhesiveness, raising the risk of thrombotic microvascular occlusion and tissue ischemia. In addition, proliferation of red blood cells, fibroblasts, and macrophages is reduced by nicotine. Carbon monoxide diminishes oxygen transport and metabolism, whereas hydrogen cyanide inhibits the enzyme systems necessary for oxidative metabolism and oxygen transport at the cellular level. Slower healing has been observed clinically in smokers with wounds resulting from trauma, disease, or surgical procedures. The reduced capacity for wound repair is a particular concern in patients undergoing plastic or reconstructive surgery. Compared with nonsmokers, smokers have a higher incidence of unsatisfactory healing after face-lift surgery, as well as a greater degree of complications following breast surgery. Smokers should be advised to stop smoking prior to elective surgery or when recovering from wounds resulting from trauma, disease, or emergent surgery.

Carbon Monoxide↗

PubMed1988

Binding site requirements for pea nuclear protein factor GT-1 correlate with sequences required for light-dependent transcriptional activation of the rbcS-3A gene.

Nuclear protein factor GT-1 binds to sequence boxes II, III, II* and III* upstream of the light-responsive pea rbcS-3A gene. We have shown previously that box II and box III are required for expression of rbcS-3A when redundant elements upstream of -170 (relative to the transcription start site) are removed. Here we present evidence that deletion and substitution mutations downstream of -170 which eliminate expression also decrease binding. Using a series of 2 bp substitution mutations we have defined a core of six residues (GGTTAA) within box II (GTGTGGTTAATATG) that are critical for binding. The most detrimental mutation for binding, which changes the double Gs to Cs, is sufficient to eliminate detectable expression in vivo when only 170 bp of 5' flanking sequences are present. The simplest interpretation of these data is that GT-1 is an activator of rbcS-3A transcription. Footprinting experiments show that GT-1 from both light-grown and dark-adapted plants binds to the same sequences in vitro. Therefore, the lack of expression of rbcS-3A in the dark is not due to the absence of GT-1. In our analysis of the sequence elements upstream of -170, we have mapped two additional GT-1 sites (boxes II** and III**) between -330 and -410. The similarities and differences among the GT-1 sites located upstream and downstream of -170 are discussed in terms of the different sequence requirements for rbcS-3A expression during development.

Base Sequence↗

PubMed1987

Fire prevention in the United States. Are the home fires still burning?

Injury and death from burns have reached epidemic levels in the United States during the past quarter-century. Yet preventive action on both local and national administrative levels has been dismally inadequate and underfunded. Identifying and recognizing both the etiologies of burn injuries and the statistical magnitude of the problem will, it is hoped, stimulate dedication of more resources and personnel to reducing the hazards of fire and the resulting loss of life, productivity, and property in the next two decades. Public education and national awareness are first steps to creation of a consumer and popular demand worthy of national action.

Adolescent↗

PubMed1978