Development of the Utah Artificial Arm

The development of a practical multifunction, electronically controlled artificial arm is an extremely complex undertaking. Various technical factors such as the limited capability of man-made components, together with problems in the development of adequate control systems, impair the ultimate performance of any prosthesis. Also, nontechnical problems in clinical, marketing, and economic areas strongly influence the potential success of any system. Consequently, the realization of a practical system with the possibility of near-term application requires simultaneous and coordinated work by personnel in a number of normally unrelated areas of medicine and engineering. The opinions of engineers, physicians, amputees, industrial entities, and institutions responsible for funding the fitting of artificial limnbs must be understood and must influence the design process. This paper begins with a discussion of the natural limb and those design objectives and compromises which govern the development of its artificial counterpart Specific details of the Utah Arm are then reviewed, along with general comments regarding the area of prosthetic limb research and application.     

Wet Reflectors in Millimeter-Wave Radiometry-Expenrment and Theory

Microwave radiometers are often required to operate under all weather conditions, including those under which an exposed surface of the antenna system becomes wetted by rain. Here we discuss the special case of a wetted flat reflector, with energy at 20.60 and 31.65 GHz linearly and orthogonally polarized at an incidence angle of 45°. The brightness temperatures produced by the wet reflector are computed from conventional theory, and are measured for various thicknesses of water layer. Both theory and experiment show that the brightness temperatures produced by the wet reflector have the same behavior throughout a range of water-layer thicknesses. The impact of these results on design of radiometers for research and operational application is discussed.     

Ractions of SiC with H2/H2O/Ar Mixtures at 1300°C

The reactions of a sintered α-SiC with 5% H₂/H₂O/Ar at 1300°C were studied. Thermomchemical modeling indicates that three reaction regions are expected, depending on the initial water vapor or equivalently oxygen content of the gas stream. A high oxygen content ( P (O₂) > 10⁻²² atm) leads to a SiO₂ formation. This generally forms as a protective film and limits consumption of the SiC (passive oxidation). An intermediate oxygen content (10⁻²² atm > P (O₂) > 10⁻²⁶ atm) leads to SiO and CO formation. These gaseous products can lead to rapid consumption of the SiC (active oxidation). Thermogravimetric studies in this intermediate region gave reaction rates which appear to be controlled by H₂O gas-phase transport to the sample and reacted microstructures showed extensive grain-boundary attack in this region. Finally, a very low oxygen content ( P (O₂) < 10⁻²⁶ atm) is thermochemically predicted to lead to selective removal of carbon and formation of free silicon. Experimentally low weight losses and iron silicides are observed in this region. The iron silicides are attributed to reaction of free silicon and iron impurities in the system.     

Present morality in parkinson's disease: the ratio of observed to expected deaths with a method to calculate expected deaths

Excess mortality, i.e. more deaths than expected in a similar normal population, has been reduced in Parkinson's disease by levodopa. A California series and a large collaborative study throughout the United States show the ratio of observed to expected deaths to be normal. In contrast, a New York study was similar patients and a Montreal group of much more severely disabled patients showed greater mortality. The reasons for these differences are unclear, but some variations in results may be attributed to different methods of calculating expected deaths to derive the ratio of observed to expected deaths.     

Effect of stable strontium on the tissue alkaline and acid phosphatase activities of rat: feeding studies

The effect of feeding stable strontium (Sr) on the tissue alkaline and acid phosphatase activities was studied in young rats. These activities were reduced in liver and small intestine by 10% to 15% at 2 weeks, 20% to 30% at 4 weeks and in kidney by 20% at 6 weeks only in rats fed 2% Sr diet; bone alkaliine phosphatase activity was, however, increased by 80% to 100% (2-6 weeks) in these rats. Gross lesions like paralysis, hemorrhage, rickets and high mortality were observed after 4 to 6 weeks. Although no such lesions were seen, appreciable changes in enzyme activities as mentioned above were discernible in rats fed 1% Sr diet for 6 weeks. Feeding of a 0.5% Sr diet for a period up to 6 weeks had no deleterious effect. Recovery following consumption of a normal diet for 2 weeks was almost complete in liver and small intestine but not in kidney. The elevated tissue Sr levels do not explain the pronounced losses seen in this investigation as compared to those in the earlier in vitro experiments. This study depicts the possible damage due to prolonged therapeutic use of large amounts of stable Sr for the removal of radiostrontium.     

Involvement of 4-hydroxymandelic acid in the degradation of mandelic acid by Pseudomonas convexa

A microorganism capable of degrading DL-mandelic acid was isolated from sewage sediment of enrichment culture and was identified as Pseudomonas convexa. It was found to metabolize mandelic acid by a new pathway involving 4-hydroxymandelic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid as aromatic intermediates. All the enzymes of the pathway were demonstrated in cell-free extracts. L-Mandelate-4-hydroxylase, a soluble enzyme, requires tetrahydropteridine, nicotinamide adenine dinucleotide phosphate, reduced form, and Fe2+ for its activity. The next enzyme, L-4-hydroxymandelate oxidase (decarboxylating), a particulate enzyme, requires flavine adenine dinucleotide and Mn2+ for its activity. A nicotinamide adenine dinucleotide-dependent, as well as a nicotinamide adenine dinucleotide phosphate-dependent, benzaldehyde dehydrogenase has been resolved and partially purified.     

Dependence of centriole formation on protein synthesis

Electron microscope observations were made of rat peroneal nerve after crushing using intravenously injected horseradish peroxidase (HRP) as a tracer protein to indicate changes in vascular permeability. At 1/2 h and 2 d after the crush there was gross leakage of HRP from damaged capillaries at the site of injury but none from vessels above or below this. Ultrastructurally vessels at the site of crush showed broken and separated endothelial cells. Proximally and distally there was little abnormal in the vessel walls; vesicles containing HRP were absent and tight-junctions between cells remained intact. Twenty-one days after the crush, leakage of HRP was found both at the site of crush and along the distal segment. The only change in vessel walls was an obvious increase in vesicles filled with HRP. Tracer was also found both in perivascular locations and throughout the endoneurial space.     

Calciphylaxis in man. A syndrome of tissue necrosis and vascular calcification in 11 patients with chronic renal failure

Eleven patients with chronic renal failure and presumed secondary hyperparathyroidism developed a syndrome of medial calcinosis of the arteries and painful ischemic ulcers of the fingers, legs, or thighs, or any combination of the three. Five patients required maintenance hemodialysis; six had functioning renal homografts. Severe hyperphosphatemia had existed in each; seven showed roentgenographic evidence of subperiosteal resorption. Similarities are evident between the lesions and experimentally produced calciphylaxix. The lesions demonstrated a relentless, progressive course, with serious morbidity and mortality. Hyperplastic or adenomatours parathyroid tissue was removed from ten of 11 patients unergoing surgical procedures; healing followed in seven patients. Treatment with phosphate-binding antacids to lower serum phosphorus levels may prevent this syndrome. Total or subtotal parathyroidectomy should be considered when ischemic skin lesions appear in uremic patients or in renal transplant recipients.     

Bilateral projection of the canine tooth pulp to bulbar trigeminal neurons

Unit activity was recorded extracellulary from neurons of the cat medulla following electrical stimulation of the ipsilateral and/or contralateral cannine tooth pulps. The majority of the cells (67%) were only responsive to ipsilateral stimulation. However, many (28%) responded to stimulation of either canine pulp and a few (5%) responsed to contralateral stimulation alone. The neurons were localized histologically in the necleus proprius of the rostral trigeminal nucleus caudalis (NVCaud) and in dorsal portions of the ventromedially contiguous lateral reticular formation (LRF). Cells exclusively responsive to ipsilateral stimuli had a relatively wide dorsoventral distribution. In contrast, 'bilateral' and 'contralateral' cells were situated only in the deep NVCaud-LRF border zone or in immediately adjacent portions of the LRF. Generally, ipsilateral stimuli evoked response bursts with shorter latencies, more spike potentials and briefer interspike intervals than equivalent contralateral stimuli. In experiments designed to study afferent interactions, a conditioning stimulus, applied to either the ipsilateral or the contralateral canine, preceded a test stimulus applied to the other canine at predetermined interstimulus intervals. Responses to the test stimulus were either totally or partially suppressed when intervals of moderate duration (90-500 msec) were used. However, responses to the test stimulus frequently were enhanced when the intervals were breif (less than or equal to 60 msec) or when the teeth were stimulated simultaneously. The results reveal that bilateral afferents from the pulps of the canine teeth converge upon neurons of bulbar trigeminal structures, that the neurons are differentially responsive to the activation of ipsilateral and contralateral pulpal receptors and that bilateral afferent barrages originating in the canine pulps interact to modulate the firing patterns of the neurons.     

Skeletal resistance to the calcemic action of parathyroid hormone in uremia: role of 1,25 (OH)2 D3

Studies were carried out to investigate the role of 1,25(OH)2D3 in the skeletal resistance to the calcemic action of parathyroid hormone. The change in serum calcium after the intravenous infusion of 2 U of parathyroid extract (PTE)/kg body wt/hr for eight hours was evaluated in thyroparathyroidectomized (T-PTX) dogs before, and one, two and three days after, induction of uremia by bilateral ureteral ligation (11 dogs) or by bilateral nephrectomy (8 dogs). In another six nephrectomized and T-PTX dogs, 0.68 ug of 1, 25 (OH)2D3/day was given on the day of nephrectomy and for two days thereafter. Serum creatinine in each day of the study was not different among the three groups. The study also included the evaluation of the effect of sham operation (five dogs) and the administration of 1,25 (OH)2D3 to dogs with normal renal function (four dogs) on the calcemic response to PTE, as well as the reproducibility of such a response in the same animal. The results showed that 1) the calcemic response to PTE was markedly impaired after one day of bilateral ureteral ligation or nephrectomy, but the impairment was more severe after nephrectomy; 2) the calcemic response to PTE after two or three days of bilateral ureteral ligation was similar to that seen at one day after nephrectomy; 3) 1, 25 (OH)2D3 partially restored the calcemic response to PTE in the nephrectomized animals to levels similar to those seen after one day of bilateral ureteral ligation; 4) sham operation did not affect the response to PTE, and repeated infusion of PTE produced similar changes in the concentrations of serum calcium. The data indicate that (a) a deficiency of 1,25 (OH)2D3 is at least partly responsible for the skeletal resistance to the calcemic action of PTH in uremia; (b) uremia, per se, may also contribute to this phenomenon; and (c) the kidney after one day of complete bilateral ureteral ligation may still produce 1,25 (OH)2D3, but this ability is compromised after two days of ureteral obstruction.