scholarly journals Calcium Efflux from Internally Dialyzed Squid Giant Axons

1973 ◽  
Vol 62 (5) ◽  
pp. 575-589 ◽  
Author(s):  
Reinaldo Dipolo
Keyword(s):  
Calcium Ions ◽  
Initial Rate ◽  
Calcium Efflux ◽  
Perfusion Technique ◽  
Giant Axons ◽  
The Mean ◽  
Per Se ◽  
Internal Sources

Calcium efflux has been studied in squid giant axons under conditions in which the internal composition was controlled by means of a dialysis perfusion technique. The mean calcium efflux from axons dialyzed with 0.3 µM calcium and 5 mM ATP was 0.26 pmol/cm2·s at 22°C. The curve relating the Ca efflux with the internal Ca concentration had a slope of about one for [Ca]i lower than 0.3µM and a slope smaller than one for higher concentrations. Under the above conditions replacement of [Na]o and [Ca]o by Tris and Mg causes an 80% fall in the calcium efflux. When the axons were dialyzed with a medium free of ATP and containing 2 mM cyanide plus 5µg/ml oligomycin, analysis of the perfusion effluent gave values of 1–4 µM ATP. Under this low ATP condition, replacement of external sodium and calcium causes the same drop in the calcium efflux. The same effect was observed at higher [Ca]i, (80 µM). These results suggest that the Na-Ca exchange component of the calcium efflux is apparently not dependent on the amounts of ATP in the axoplasm. Axons previously depleted of ATP show a significant transient drop in the calcium efflux when ATP is added to the dialysis medium. This effect probably represents the sequestering of calcium by the mitochondrial system. The consumption of calcium by the mitochondria of the axoplasm in dialyzed axons was determined to be of the order of 6.0 x 10-7 mol Ca++/mg of protein with an initial rate of 2.6 x 10-8 mol Ca++/min·mg of protein. Axons dialyzed with 2 mM cyanide after 8–10-min delays show a rise in the calcium efflux in the presence of "normal" amounts of exogenous ATP. This effect seems to indicate that cyanide, per se, can release calcium ions from internal sources.

scholarly journals Effect of ATP on the Calcium Efflux in Dialyzed Squid Giant Axons

1974 ◽  
Vol 64 (4) ◽  
pp. 503-517 ◽  
Author(s):  
Reinaldo DiPolo
Keyword(s):  
Transport System ◽  
Calcium Transport ◽  
Artificial Seawater ◽  
Ionized Calcium ◽  
Calcium Efflux ◽  
Perfusion Technique ◽  
Virtual Absence ◽  
Giant Axons ◽  
The Mean

Dialysis perfusion technique makes it possible to control the internal composition of squid giant axons. Calcium efflux has been studied in the presence and in the virtual absence (<5 µM) of ATP. The mean calcium efflux from axons dialyzed with 0.3 µM ionized calcium, [ATP]i > 1,000 µM, and bathed in artificial seawater (ASW) was 0.24 ± 0.02 pmol·cm-2·s-1 (P/CS) (n = 8) at 22°C. With [ATP]i < 5 µM the mean efflux was 0.11 ± 0.01 P/CS (n = 15). The curve relating calcium efflux to [ATP]i shows a constant residual calcium efflux in the range of 1–100 µM [ATP]i. An increase of the calcium efflux is observed when [ATP]i is >100 µM and saturates at [ATP]i > 1,000 µM. The magnitude of the ATP-dependent fraction of the calcium efflux varies with external concentrations of Na+, Ca++, and Mg++. These results suggest that internal ATP changes the affinity of the calcium transport system for external cations.

On the Mechanism by which Cell Contact Induces the Release Reaction of Blood Platelets; the Effect of Cationic Polymers

1972 ◽  
Vol 27 (01) ◽  
pp. 121-133 ◽  
Author(s):  
P Massini ◽  
E. F Lüscher
Keyword(s):  
Human Blood ◽  
Calcium Ions ◽  
Blood Platelets ◽  
Cell Contact ◽  
Second Phase ◽  
Cationic Polymers ◽  
Release Reaction ◽  
Per Se ◽  
Human Blood Platelets

SummaryHuman blood platelets are aggregated by the basic polymers polylysine and DEAE- dextran. Under certain conditions a second phase of aggregation, concomitant with the release reaction, is elicited. The presence of ADP, calcium ions and a plasmatic cofactor within the primary aggregates are necessary for the induction of the release reaction. These experiments demonstrate that cell contact per se does not lead to a release reaction ; in order to become effective it must take place in the presence of ADP.

COMBINING ABILITY FOR INHERITANCE OF ECONOMIC TRAITS IN OPIUM POPPY (Papaver somniferum L.)

2011 ◽  
Vol 24 (2) ◽  
pp. 01-08
Author(s):  
B. Kumar ◽  
N. K. Patra
Keyword(s):  
Combining Ability ◽  
Diallel Cross ◽  
Papaver Somniferum ◽  
Opium Poppy ◽  
Economic Traits ◽  
Degree Of Dominance ◽  
Parental Material ◽  
The Mean ◽  
Per Se ◽  
Important Medicinal Plant

Opium poppy (Papaver somniferum L.) is an important medicinal plant produces more than 80 alkaloids obtained from the capsules and straw of the plant. The estimate of combining ability gives an indication of the genetic behaviour of the parental material. It is therefore, desirable to select the parents for hybridization on the basis of their per se performance and combining ability effects. The F1, F2 and their reciprocals of an eight parent diallel cross in opium poppy were studied for combining ability of seven economic traits. The mean sum of squares due to GCA, SCA and reciprocals were significant for all the traits. The magnitude of GCA variances were invariably higher than those of SCA and thus indicating the preponderance of non-additive genetic variances, which was further affirmed by the measure of average degree of dominance i.e. ?(?2s/? 2g).  Among the parents VN35I for plant height, Sanchita and VG26 for capsules per plant, VN23, VN35I and Vivek for capsule index, VG26 and Sanchita for seed and straw yield per plant, and VN35I and VG20 for morphine content were found good general combiners. Earliness being a desired trait, parent VG20 having significant negative GCA estimates coupled with per se performance can be considered as good general combiner for early flowering. Inclusion of good general combiners in a multiple crossing program or an inter-mating population involving all possible crosses among them subjected to bi-parental mating may be expected to offer maximum promise in breeding for economic traits.DOI: http://dx.doi.org/10.3329/bjpbg.v24i2.17000

Calcium efflux in giant axons

1967 ◽  
Vol 135 (2) ◽  
pp. 368-370 ◽  
Author(s):  
M. Luxoro ◽  
S. Rissetti
Keyword(s):  
Calcium Efflux ◽  
Giant Axons

scholarly journals Relative Rates of Gluten Digestion by Nine Commercial Dietary Digestive Supplements

2021 ◽  
Vol 8 ◽  
Author(s):  
Gregory John Tanner
Keyword(s):  
Amino Acids ◽  
Celiac Disease ◽  
Initial Rate ◽  
Relative Rate ◽  
Elisa Method ◽  
Fasting Stomach ◽  
The Mean ◽  
Stomach Volume ◽  
The Impact

Endopeptidases containing supplements may digest gluten and reduce the impact on celiac and gluten-sensitive subjects who inadvertently consume gluten. We investigated the relative rate of disappearance of coeliac relevant epitopes in extracts of nine commercial supplements, using two competitive enzyme-linked immunosorbent assays (ELISAs)—Ridascreen (detects QQPFP, QQQFP, LQPFP, and QLPFP) and Gluten-Tec (detects Glia-α20 and PFRPQQPYPQ). All epitopes are destroyed by cleavage after P and Q amino acids. Rates at pH 3.5 and pH 7.0 were measured. These experiments were designed to measure relative rates of epitope digestion not to mimic in vivo digestion. The supplements were: 1 GluteGuard, 2 GlutenBlock, 3 GliadinX, 4 GlutnGo, 5 GlutenRescue, 6 Eat E-Z Gluten+, 7 Glutenease, 8 Glutezyme, and 9 Gluten Digest. The mean initial rate and half-lives of epitope digestion were deduced and extrapolated to rates at the recommended dose of one supplement in a fasting stomach volume. At pH 7, supplement 1 was the fastest acting of the supplements, with Ridascreen ELISA, more than twice as fast as the next fastest supplements, 5, 6, 7, and 8. Supplements 2, 3, and 4 showed little activity at pH 7.0. Supplement 1 was also the fastest acting at pH 7 with Gluten-Tec ELISA, more than three times the rate for supplements 2 and 3, with supplements 4–9 showing minimal activity. At pH 3.5, supplement 1 acted more than five times as fast as the next fastest supplements, 2 and 3, when measured by Ridascreen, but supplements 2 and 3 were over two times faster than supplement 1 when measured by Gluten-Tec. Supplements 4–9 demonstrated minimal activity at pH 3.5 with either ELISA. Supplement 1 most rapidly digested the key immuno-reactive gluten epitopes identified by the R5 antibody in the Codex-approved competitive Ridascreen ELISA method and associated with the pathology of celiac disease.

Effect of 1,25-(OH)2D3 on jejunal absorption of magnesium in patients with chronic renal disease

1980 ◽  
Vol 238 (4) ◽  
pp. G349-G352 ◽  
Author(s):  
A. C. Schmulen ◽  
M. Lerman ◽  
C. Y. Pak ◽  
J. Zerwekh ◽  
S. Morawski ◽  
...  
Keyword(s):  
Vitamin D ◽  
Renal Disease ◽  
Chronic Renal Disease ◽  
Normal Subjects ◽  
Mean Value ◽  
Normal Serum ◽  
Perfusion Technique ◽  
Dihydroxyvitamin D3 ◽  
Jejunal Absorption ◽  
The Mean

These studies were performed to see if jejunal malabsorption of magnesium in patients with chronic renal disease was influenced by therapy with 1 alpha, 25-dihydroxyvitamin D3 [1,25-(OH)2D3; 2 microgram/day by mouth for 7 days]. This treatment restored normal serum concentrations of the vitamin D metabolite from 0.9 +/- 0.2 to 4.2 +/- 0.6 ng/dl. Jejunal absorption of magnesium, measured by a triple-lumen constant-perfusion technique, was enhanced in each of the seven patients by this therapy. The mean value rose from 0.04 +/- 0.02 to 0.13 +/- 0.02 mmol . 30 cm-1 . h-1. This last value is similar to the magnesium absorption rate in untreated normal subjects. These results demonstrate that magnesium absorption in the human jejunum is dependent on vitamin D, and they show that 1 alpha,25-dihydroxyvitamin D3 therapy in patients with chronic renal failure is associated with an enhanced jejunal absorption of magnesium.

The effect of body size and body condition on the ovulation rate of ewes

1977 ◽  
Vol 24 (3) ◽  
pp. 377-385 ◽  
Author(s):  
M. J. Ducker ◽  
J. S. Boyd
Keyword(s):  
Body Size ◽  
Breeding Season ◽  
Body Condition ◽  
Live Weight ◽  
Ovulation Rate ◽  
Subjective Measure ◽  
Body Dimensions ◽  
The Mean ◽  
Per Se ◽  
Linear Body

SUMMARYBody size was estimated for 255 Greyface ewes using five linear body dimensions. On the basis of this calculated measure combined with a subjective measure of body size 50 small and 50 large ewes were selected for use in the experiment. Precise ovulation data were obtained by endoscopy and this technique allowed the ewes to be mated subsequently.Body size did not affect the mean ovulation rate of the ewes although, at the same level of body condition, the large ewes were 25% heavier than the small ewes. The ovulation rates and the numbers of lambs born were influenced by changes in live weight and body condition. For these reasons live weight per se was not a good indicator of ovulation rate as ewe live weight was a combination of both body size and body condition. At the same live weight small ewes in improving body condition had a significantly higher ovulation rate than large ewes in reducing body condition.The onset of the breeding season of the ewes was not affected by their body size. The mean date of onset of oestrous activity for both large and small ewes was 17 October 1972 at a latitude 55° 52′ N.

Activity and energy expenditure in laying hens: 3. The energy cost of eating and posture

1976 ◽  
Vol 87 (1) ◽  
pp. 85-88 ◽  
Author(s):  
M. Van Kampen
Keyword(s):  
Energy Expenditure ◽  
Spontaneous Activity ◽  
Heat Production ◽  
Energy Cost ◽  
Laying Hens ◽  
The Mean ◽  
Per Se ◽  
The Difference

SummaryThe influence of standing, spontaneous activity and eating on heat production was determined.The extra heat production of standing is negatively correlated with the length of standing period. In a short standing period of 30 min the associated activity, pecking against the respirometer wall and fluffing the feathers, was high and the heat production was increased by 25% compared with that during sitting. After standing for 1½ h spontaneous activity was very low and the difference in heat production between the standing and sitting bird was reduced by 9%.During eating the heat production increased by an average of 37% (range 11–68%); this was due mainly to the act of eating per se and not to the work of digestion.The mean energy cost of eating was calculated to be 143 J/kg0·75/min spent eating.

Pigment Production From Tyrosine by Australian Isolates of Phytophthora Species

1976 ◽  
Vol 24 (5) ◽  
pp. 607 ◽  
Author(s):  
CJ Shepherd
Keyword(s):  
Casein Hydrolysate ◽  
Phytophthora Species ◽  
Pigment Production ◽  
Native Vegetation ◽  
Preliminary Screening ◽  
Morphological Criteria ◽  
Phytophthora Drechsleri ◽  
Taxonomic Criterion ◽  
The Mean ◽  
Per Se

Pigment production from tyrosine by 138 isolates of 12 Australasian species of Phytophthora was followed photodensitometrically. Optimal production occurred on a casein hydrolysate-tyrosine medium at pH 6.0, when sugars were absent. The mean pigment production of northern ecotype isolates of Phytophthora drechsleri ( = P. cryptogea) was significantly greater than that of southern ecotype isolates, and the mean pigment production of A1 compatibility type isolates of P. parasitica was approximately double that of A2 type isolates. Little or no pigment was produced by any of the isolates of P. cinnamomi examined. While pigment production, per se, appears to be a poor taxonomic criterion, it is suggested that the degree of pigment production by unknown isolates might in some cases prove helpful as a confirmatory characteristic following species identification by morphological criteria, and as a preliminary screening technique particularly applicable to the recognition of P. cinnamomi among Phytophthora isolates obtained from native vegetation in Australia.

Sign in / Sign up

Export Citation Format

Share Document