Amino Acid Transport in Pseudomonas aeruginosa

Properties of the transport systems for amino acids in Pseudomonas aeruginosa were investigated. Exogenous (14)C-labeled amino acids were shown to equilibrate with the internal native amino acid pool prior to incorporation into protein. When added at low external concentrations, the majority of the amino acids examined entered the protein of the cell unaltered. The rates of amino acid transport, established at low concentrations with 18 commonly occurring amino acids, varied as much as 40-fold. The transport process became saturated at high external amino acid concentrations, was temperature-sensitive, and was inhibited by sodium azide and iodoacetamide. Intracellular to extracellular amino acid ratios of 100- to 300-fold were maintained during exponential growth of the population in a glucose minimal medium. When the medium became depleted of glucose, neither extracellular nor intracellular amino acids could be detected.     

Amino Acid Pool Formation in Pseudomonas aeruginosa

The accumulation and behavior of various amino acids in the pool of Pseudomonas aeruginosa (ATCC 9027) were investigated. Patterns of pool formation and maintenance varied with different amino acids tested and were dependent, to a considerable extent, upon the ability of the organism to catabolize the particular amino acid. The establishment of steady-state amino acid pool levels depended upon the activity of the amino acid permease involved and upon the rate of protein synthesis. The presence of a relatively large specific amino acid pool did not affect the formation of a pool of a structurally different amino acid, and a preformed steady-state pool was not displaced by structurally unrelated amino acids. Steady-state amino acid pools decreased rapidly in the presence of inhibitors of energy metabolism and at 0 C. Steady-state internal amino acid pools were found to be in equilibrium with the corresponding external amino acid, present at low levels. A multiplicity of proline pools was demonstrated.     

Epizootic characteristics of hepatic and renal lesions in English sole, Parophrys vetulus, from Puget Sound

English sole, Parophrys vetulus , from eight locations within Puget Sound, U.S.A. were examined for histological abnormalities of the liver and kidney. A total of 1083 fish were collected between February 1979 and June 1984 in nine separate sampling periods. Idiopathic lesions, i.e. lesions of unknown cause, were classified into eight hepatic and four renal lesion categories. The significance of certain potential risk factors associated with lesion prevalences, including age, gender, site of capture, season of capture and year of capture, were assessed by logistic regression. The odds ratios for the significant risk factors were also calculated. Site of capture and age of the examined fish were found to be the most important factors for most of the observed lesion types, e.g., hepatic neoplasms and foci of cellular alteration, whereas year and season of capture were significant influences for only a few lesion types, e.g., specific and nonspecific degenerative/necrotic lesions of the liver. Gender of examined fish was not found to be a significant factor for any of the lesion types. These results emphasize the importance of including certain potential influences, such as age and season of capture, in the analysis of field-collected organ pathology data.     

Estimation of blood flow distribution in skeletal muscle from inert gas washout

A new method is evaluated for the estimation of blood flow-to-volume distribution in skeletal muscle from inert gas washout kinetics. Acetylene washout from the isolated, blood-perfused canine gracilis muscle was measured continuously with a blood gas catheter in combination with a mass spectrometer. The washout curves were transformed to flow-to-volume ratio distributions by means of a 50-compartment model. The algorithm fits the expression for the washout curve derived from the model by a least-squares method with enforced smoothing. The algorithm was evaluated using computer simulations in which artificial washout curves were generated by a multicompartment model with a known flow distribution. A wide range of given flow distributions could be recovered from the simulated data. The data were also analyzed using a linear programming technique. Analysis of the experimental data with the least-squares method showed that there is considerable heterogeneity in the distribution of perfusion in resting gracilis muscle. The distribution is characterized by at least two modes and a single compartment with a very low perfusion-to-volume ratio. Experimental noise made it impossible to obtain feasible flow distributions by means of linear programming.     

Error due to dead-space admixture in single-breath method for estimation of pulmonary blood flow

The single-breath method of Kim et al. (J. Appl. Physiol. 21: 1338-1344, 1966) for the estimation of pulmonary blood flow is based on a single-alveolus lung model for which an analytical relationship has been established between the kinetic behavior of the alveolar O2 and CO2 tensions and the pulmonary blood flow. The analysis is based on the assumption that the dead-space contribution to the expirate is negligible after expiration of a predefined volume. We have examined the influence of this assumption on the estimation of pulmonary blood flow by computer simulation in a lung model that incorporates deadspace contribution to the expirate. Data on the fractional contribution of the dead space to the expired gas were obtained from Tsunoda et al.'s study (J. Appl. Physiol. 32: 644-649, 1972) on the emptying pattern of normal adult lungs. The results show that failure to take account of the dead-space contribution can cause an underestimation in the pulmonary blood flow of greater than 30%. The error can be reduced by ignoring the first part of the expiration but only at the cost of an increase in the sensitivity of the single-breath method to measurement noise. This property of the system is demonstrated experimentally. The error due to dead-space admixture depends on the total volume of dead-space gas, the measurement noise, the pulmonary blood flow, and the emptying characteristics of the dead-space compartment during expiration. In normal subjects it is possible to optimize the experimental design so that the systematic error is less than 5% and the coefficient of variation is less than 10%.(ABSTRACT TRUNCATED AT 250 WORDS)     

The frequency, distribution, and pathology of three diseases of demersal fishes in the Bering Sea

During September and October, 1975, bottom-dwelling fish from the Bering Sea were examined for diseases. The three most commonly observed diseases and their frequency of occurrence were epidermal papillomas of rock sole ( Lepidopsetta bilineata Ayres), 1-0%; lymphocystis of yellowfln sole ( Limanda aspera Pallas), 2-1 %; and epidermal tumours of the pseudobranch of adult Pacific cod ( Gadus macrocephalus Tilesius), 7-4%. Both the appearance and the histological characteristics of epidermal papillomas on rock sole resembled those found on several species of flatfish in Puget Sound. The frequency of tumour-bearing rock sole ranged from 0-23%, with the highest occurrence at sampling stations around the periphery of the Bering Sea in water depths of 20-30 fathoms (36-54 m). The virus-caused lymphocystis lesions were usually on the 'blind' side fins and skin surfaces of yellowfin sole, the largest lesions being found on the operculum, and the most common site of infection was the pectoral fin. The frequency of lymphocystis was 0-15 %, with a gradual increase of prevalence from the northern to southern sampling stations. The Pacific cod tumours were always bilateral, and contained remnants of normal-appearing pseudobranchial tissue on the surface or deep inside the tumours. Portions of some tumours were necrotic and liquefied. Tumour-bearing cod were most commonly found in the south and south-eastern Bering Sea and the frequency of affected cod ranged from 0-100%.     

Enzymatic Degradation of Ribosomes During Endogenous Respiration of Pseudomonas aeruginosa.

Gronlund, Audrey F. (University of British Columbia, Vancouver, B.C., Canada), and J. J. R. Campbell. Enzymatic degradation of ribosomes during endogenous respiration of Pseudomonas aeruginosa. J. Bacteriol. 90:1-7. 1965.-From sedimentation analyses it was found that the ribosomal content of Pseudomonas aeruginosa decreased during endogenous respiration. A greater degree of degradation of 50S than 30S ribosomes occurred during the 3-hr starvation period. The enzyme responsible for the initiation of ribosome degradation and present in the ribosome fraction was identified as polynucleotide phosphorylase. The enzyme was inactive in intact 70S ribosomes, but was active in low magnesium ion concentrations which allowed the 70S ribosome to dissociate. Polynucleotide phosphorylase was not solubilized after dissociation of the 70S particle, but remained firmly attached to the 50S and 30S ribosomes, the ribonucleic acid of which served as substrate.