摘要:

AbstractRabbit psoas muscle fibers, extracted in 50% (w/v) glycerol for 20 hours, concentrate up to 300 μmol calcium per gm protein when placed in a suitable electrolyte environment at pH 6.5 containing ATP and47Ca in the form of a Ca/EGTA metal buffer system. This property is retained at [Ca++] down to 2 × 10−8M, the lowest studied. The kinetics of Ca pickup are consistent with a mathematical model based on diffusion of Ca as the rate‐limiting factor. The pickup is dependent upon ATP and is increased by inclusion of CP or PEP. It is promoted by oxalate, fluoride, phosphate and pyrophosphate, which share the property of forming relatively insoluble calcium salts. Ability to concentrate calcium disappears on prolonged extraction in glycerol and after preincubation with desoxycholate.These properties are similar to those previously described for a granular fraction of muscle homogenates, and it is concluded that both are probably attributable to functional remnants of sarcoplasmic reti

ISSN:0095-9898    

DOI:10.1002/jcp.1030650202

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractAn effort has been made to ascertain the site of calcium uptake in rabbit psoas muscle by electron microscopy. Following a brief glycerol extraction, small groups of fibers were exposed in a suitable electrolyte environment to calcium and ATP. Conditions were such that calcium was accumulated as an insoluble oxalate salt. Conventional preparatory procedures for electron microscopy were modified so that the calcium oxalate deposits were retainedin situin ultrathin sections. These were found localized in the longitudinal component of the sarcoplasmic reticulum including the terminal dilatations which form the outer elements of the triads. The possible participation of the intermediate element of the triad in the uptake of calcium could not be determined. The results are regarded as direct evidence that the sarcoplasmic reticulum is intimately concerned with the uptake and release of calcium associated with the contraction‐relaxation cycl

ISSN:0095-9898    

DOI:10.1002/jcp.1030650203

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractEfferent spikes were recorded from the nerves supplying the papilla amphibiorum, ampullae, and lateral‐line neuromasts of the mudpuppy (Necturus maculosus). Increased efferent activity was associated with rotatory, vibratory, and tactile stimulation and gill movements. In a single experiment it was possible to record efferents from the nerve to the papilla basilaris of a leopard frog (Rana pipiens). The function of acoustico‐lateralis efferents is not restricted to or closely associated with a single habit, habitat, phylogenetic group, or acoustico lateralis receptor. It seems likely that all acoustico‐lateralis receptors in all vertebrates receive efferent

ISSN:0095-9898    

DOI:10.1002/jcp.1030650204

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractA method for the tissue culture of salivary glands ofSciara coprophilain a chemically defined medium is presented. When the chromosomes of the posterior lobe of the gland have puffs and the chromosomes of the anterior lobe do not have puffs prior to culture, puffs will develop in the anterior lobe chromosomes within a 24 hour culture period. When these chromosome II puffs are at their largest, fully extended state and a bulb on chromosome III is in a larva nearing pupation, the puffs and bulb become condensed in culture more rapidly than in normal development. This condensed state of the chromatin is thought to be heterochromatin. The uptake of tritiated thymidine was compared in homologous glands of 20 larvae in six different stages of development and all glands were labeled before and after culture, indicating that the culture method does not interfere with DNA synthesis.

ISSN:0095-9898    

DOI:10.1002/jcp.1030650205

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractThe growth rhythm in several strains of “clock” mutants ofNeurospora crassahas been observed to have several unusual non‐circadian characteristics. The period may range between 18 and 110 hours, depending upon strain and environmental condition. The phase of the rhythm, even when its period is 24 hours, is not related to a specific time of day, nor is it “set” or phased by light‐dark cycles. Instead, the phase can be set by transfer to fresh medium; moreover, its specific chemical composition influences the length of the period. The period is significantly influenced by temperature; the growth rate is a different function of temperature. All the strains show striking similarities in the functional dependence of period and growth rate on temperature, even though the absolute magnitudes di

ISSN:0095-9898    

DOI:10.1002/jcp.1030650206

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractThe transmembrane electrical properties of the crustacean axon have been examined by a new technique which allows for quantitative evaluation of the electrical and excitable characteristics across a microscopic area, “patch,” of fiber membrane using external electrodes. Data from repetitive firing and from non‐repetitive firing fibers compare as follows: (1) Membrane potential, resting, 82 mv repetitive; 67 mv non‐repetitive; 70–75 mv transition level repetitive to non‐repetitive. (2) Membrane potential, active, 132 mv, 50 mv overshoot repetitive; 100–120 mv, 30–50 overshoot, non‐repetitive. (3) Membrane resistance, 7.6 × 106ohms or 2300 ohms cm2repetitive; 2.8 × 106ohms or 880 ohms cm2non‐repetitive. (4) Membrane time constant, 2.5 ms repetitive; 1.5ms non‐repetitive. (5) Membrane capacity 1.0μfrepetitive; 1.7 μfnon‐repetitive. (6) Repetitive firing property may be restored to non‐repetitive axons by increasing the Vmvalue with a polarizing inward current. This increases Rmalso. (7) Non‐repetitive fibers show considerable inactivation, give rise to “more or less” spikes particularly during refractory period following a spike, and respond to anode‐break stimulation. Repetitive firing axons do not. (8) The action potential has two active components, one to depolarize (sodium) one to repolarize (potassium), both of which drive the membrane potential. toward predetermined levels. (9) The repetitive firing axons show little or nc inactivation with weak prolonged depolarization producing trains of spikes. There is a slow rise in critical firing level which ultimately causes the spike train termination. There is a slow increase in the undershoo

ISSN:0095-9898    

DOI:10.1002/jcp.1030650207

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractThe effects of sodium, calcium, potassium (magnesium), potassium, and hydrogen (pH) ion concentration in the external medium on the repetitive response and the transmembrane electrical parameters of the crustacean axon have been investigated. (1) The action potential is reduced with decrease in sodium ion concentration, the relationship is linear if the spike voltage is plotted against the log (Na0). The action potential amplitude does not increase significantly, above 135 mv, attained at Na0= 452 mM, if Na0is increased. (2) The repetitive response and oscillatory activity in general disappears as the sodium concentration is reduced to less than 150 mM. (3) The critical firing level increases with decrease in sodium, the relationship linear with respect to log (Nao). (4) The positive after potential amplitude is not affected by the sodium concentration. (5) The membrane resistance is not affected by sodium concentration. (6) Calcium lack results in decreased critical firing level and spontaneous firing, followed by a total and irreversible loss of excitability. The membrane resistance is markedly decreased. Polarizing current, if applied early after the onset of the calcium lack effect, may restore, at least partially, the excitability phenomenon. (7) Calcium excess increases membrane resistance, depresses excitability. Calcium concentration of 150 mM abolishes the repetitive response. (8) There is a 3.3+: 1 ratio Na:Ca for threshold level of repetitive response. Lower ratio figures, by reducing Na or increasing Ca or both, eliminates repetition. Increasing the ratio figure by increasing sodium or decreasing calcium or both augments oscillatory activity. This ratio is constant between the limits 400 mM Na:125, Ca to 90 mM Na:25 mM Ca. (9) Magnesium may substitute for calcium, the Na:Mg ratio for repetitive response threshold is 3.3:2. (10) Repetitive firing may be elicited over a wide range of pH values 4.2–10.5; membrane potential and resistance values decline invariably at pH values above 9.5 and below 4.5. (11) Repetitive firing is enhanced by increasing pH values, depressed by reducing pH values. (12) Effect of excess potassium produces depolarization, reduced membrane resistance, inactivation and abolition of repetitive firing, may be relieved by applied hyperpolarization. (13) Potassium lack results in membrane potential and resistance irreversible decline, permanent inactivation, total loss of excitability. Partial restoration by strong hyperpolarization if applied before effect is complete. Potassium replacement in solution only slows or temporarily arrests the overall membrane deterioration. (14) Conclusions ‐ sodium controls spike, potassium controls after potential, calcium (magnesium) controls membrane permeability, pH controls amount of available ionized calcium. Repetitive firing requires proper ratio 3.3/1 of (Nao)/(Ca0), pH above 7.6 and potassium at 15 mM in solut

ISSN:0095-9898    

DOI:10.1002/jcp.1030650208

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractThe distribution of infectious virus particles in various tissues of the mouse was determined following the intraperitoneal injection of three plaque variants of Mengo encephalomyelitis virus. When lethal doses were administered, virus appeared first in the spleen and lymph nodes (suggesting that these are the primary target organs for the agents), followed by its appearance in spinal cord and brain, in which tissues the infectious titers increased progressively until the death of the animals. Low levels of virus were sometimes found in lung, heart and kidney at 24–48 hours post‐challenge, but disappeared from these tissues at later times. Virus was never detected in blood or liver, suggesting that the virus moves throughout the animal by way of the lymphatic system. When sub‐lethal doses of virus were injected, it was detectable only in spleen and lymph nodes, and disappeared from these tissues by 8–9 days post‐challenge.The LD50'sfor the three variants when injected by both the intraperitoneal and intracerebral routes were determined. The I.P.‐LD50'sfor the L (large plaque former), M (medium plaque former) and S (minute plaque former) variants in 14–16 gm mice were found to be 1, 1–5 × 104and 2–10 × 104p.f.u.'s, respectively. The I.C.‐LD50'swere essentially the same (1–5 p.f.u.'s) for all three variants. The possibility that the differences in the I.P.‐LD50'smay be due to differences in the abilities of the variants to stimulate interferon production or in their sensitivities to its anti

ISSN:0095-9898    

DOI:10.1002/jcp.1030650209

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractTen adult western gulls (Larus occidentalis) ranging in weight from 761–1,004 gm were studied. The gulls were fed 3% NaCl in their drinking water. They were killed by decapitation, and the salt glands, weighing 0.51–0.78 gm were cooled, homogenized in 0.14 M KCl, centrifuged at 0–4°C at 20,000 × G for 30 minutes and the supernatant used for all enzymes assays. All assays were conducted at 25°C by observing the changes in absorbancy with time using a Gilford Multiple Absorbance Recorder. The enzymes were assayed by measuring either the appearance or disappearance of NADH or NADPH at 340 mμ. The average units of enzyme activity (the amount of enzyme required to form 1 μM of substrate per minute ) per gram of salt gland were as follows: phosphoglucomutase, 0.62; glucose‐6‐phosphate dehydrogenase, 1.40; aldolase, 2.86; lactic dehydrogenase, 90.1; isocitric dehydrogenase, 5.08; malic enzyme, 0.92; glutamic‐oxaloacetic transaminase, 100.5; and glutamic‐pyruvic transaminase, 0.50. The protein content of the salt glands varied from 62.5–87.6 mg protein/gm. On the basis of an adjusted calculation of energy yields from the glycolytic scheme and the Krebs cycle, it would appear that only one‐third of the energy derived from these pathways would be necessary to maintain the maximum rate of salt secretion, leaving the other two‐thirds for other cellular processes. Glutamate metabolism may also be important as an energy

ISSN:0095-9898    

DOI:10.1002/jcp.1030650210

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY

摘要:

AbstractThe entrance of carbohydrates into the cells of C.luciliaehas been studied, using the non‐utilizable monosaccharides: L‐sorbose, D‐xylose, L‐xylose, D‐arabinose, L‐arabinose, L‐rhamnose, D‐lyxose, D‐2‐deoxyglucose, and L‐fucose; all nine sugars entered the cell. At 0.5 mM external concentration the rate of increase in intracellular concentration is constant for all sugars until the intracellular concentrations equal or exceed the extracellular concentration. At 20 mM external concentration, the rate of increase of intracellular concentration decreases continuously and the maximum intracellular concentration never exceeds the extracellular concentration. There is competition between monosaccharides presented simultaneously to the cells and the transport mechanism shows enormously greater affinity for glucose than for other monosaccharides. The rate of carbohydrate entrance is inhibited 50% and 70% by KCN(10−4M) and DNP(10−5M) respectively at 0.5 mM external concentrations. However, these inhibitors do not affect transport from external concentrations of the order of 0.02 M. These data are interpreted as indicating two mechanisms for carbohydrate entrance: (a) an active transport mechanism, active at low external concentration and dependent upon a supply of metabolic energy; (b) facilitated diffusion, of importance only at high external concentrations. These results are compared with those reported in the literature

ISSN:0095-9898    

DOI:10.1002/jcp.1030650211

出版商:The Wistar Institute of Anatomy and Biology    

年代:1965

数据来源: WILEY