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Biomedical subjects

M W Marshall

Publications and source records attributed to M W Marshall.

At least 37 records · Page 2Linked to original sources
PubMed1988

Effects of low fat diets differing in degree of fat unsaturation on plasma lipids, lipoproteins, and apolipoproteins in adult men.

The effects of two low fat diets with differing ratios of polyunsaturated to saturated fatty acids (P/S) on blood lipids, lipoproteins (LP), and apolipoproteins (Apo) were studied in 23 adult men, 30-60 years old, using a crossover design. Both test diets had 25% fat calories with either a P/S of 0.3 (Diet 1) or a P/S of 1.0 (Diet 2) and equivalent amounts of cholesterol. The study consisted of four periods: a 5-week prestudy on self-selected diet (SS), two 6-week test diet periods followed by a second 5-week post-study period on the SS diet. When compared with the SS diet, Diet 2 lowered the mean plasma total cholesterol (TC) by about 20% (P less than 0.01). Low density lipoprotein (LDL) cholesterol was also decreased by about 18% by Diet 2 (P less than 0.01). The high P/S diet did not cause a change in total cholesterol in the high density lipoprotein (HDL) subclass2 (HDL2) when compared to the SS diet. Levels of triglycerides (TG) were slightly reduced in HDL2 but showed a greater reduction in HDL3 in both diets. Phospholipids (PL) were significantly reduced in HDL2 and in HDL3, but the reduction in HDL3 PL was not statistically significant. Apo A-I levels were not changed by either diet when compared with the SS diet, but Apo A-II levels of HDL2 and HDL3 were significantly decreased by the low fat diets, and there was no P/S effect. No other consistent changes in apoprotein levels occurred. Our data suggest that, in men with normal lipid levels, practical dietary changes involving a moderate increase in P/S from 0.3 to 1.0 in a low fat, low cholesterol diet do influence lipoprotein composition and apoprotein distribution in a short time. The reduction in cholesterol in total lipid composition and in LDL lipids which accompanied the reduction of dietary fat and cholesterol are considered to be beneficial.

Adult↗
PubMed1988

Enlarging soft tissue mass involving the mandibular left alveolar ridge.

The central giant-cell granuloma is a benign, fairly uncommon lesion that can appear clinically and radiographically similar to many other lesions. When histopathological examination discloses a giant-cell lesion of bone, clinical, radiographic, and laboratory data must be obtained and carefully analyzed to rule out such conditions as hyperparathyroidism, Paget's disease, and cherubism, and to confirm the diagnosis of central giant-cell granuloma. Once the diagnosis is established, thorough curettage or surgical excision of the tumor is recommended to assure complete removal. Although recurrence is rare, periodic postoperative examination is also suggested.

Aged↗
PubMed1987

Dietary linoleate increases fluidity and influences chemical composition of plasma low density lipoprotein in adult men.

Dietary linoleate was effective to increase LDL fluidity in adult men but did not significantly influence VLDL or HDL fluidities. Lipoproteins were isolated ultracentrifugally from plasma of sixteen healthy, free living male volunteers consuming controlled diets formulated from typical U.S.A. foods to have 35 energy % fat with 10 g (diet L) or 30 g (diet H) linoleate per day, 30-50 g saturated fatty acids/day and the balance mainly monounsaturated fatty acids. Calculated cholesterol intakes were 500 mg/day at each calorie level. Changes in LDL fluidity were detected as differences in diphenylhexatriene (DPH) fluorescence polarization upon crossover between the two controlled diets. Thermotropic measurement of DPH fluorescence anisotropy and compositional analyses indicated that LDL and HDL fluidities were dependent upon phospholipid and triacylglycerol concentrations, respectively, and were modulated by the presence of cholesteryl esters. Fatty acid analyses of the major lipid classes of the isolated lipoproteins indicated that changes, upon diet crossover, in DPH fluorescence anisotropy, were a linear function of the incremental change in LDL phospholipid linoleate. The fluorescent probe described an environment corresponding to the fatty acyl moieties of the phospholipids on the LDL periphery, which composition is apparently under dietary control. It is suggested that the diet induced fluidity changes may affect the conformation of the apoprotein moiety on the LDL surface and thus the potential for LDL interaction with cellular LDL receptors.

Adult↗
PubMed1986

Effects of low fat diets varying in P/S ratio on nutrient intakes, fecal excretion, blood chemistry profiles, and fatty acids of adult men.

Twenty-three apparently healthy volunteers aged 35 to 60 years consumed closely monitored self-selected (SS) diets for five weeks followed by two low fat controlled diets (25% energy) for two six-week periods followed by another five-week SS diet. The two low fat diets, fed in a crossover design to one-half of the subjects per controlled diet period, had a polyunsaturated/saturated (P/S) fat ratio of either 0.3 or 1.0. Results are reported for bi-weekly measurements of energy and nutrients; blood profiles and plasma fatty acids; and for end-of-period values for stool characteristics. Blood chemistry profiles differed in the two groups. The low P/S diet produced significant increases not only in cholesterol, but in 16:0, 16:1, and percent saturated fatty acids and decreases in 18:2 and omega 6 fatty acids. The reverse was seen with the high P/S diet. The essential fatty acid (EFA) linoleic acid returned in the poststudy period to prestudy levels (all subjects), but arachidonic acid did not. The explanation for negative correlation between magnesium intake or excretion and percent plasma linoleic acid must await further research.

Adult↗
PubMed1986

Self-selected vs. controlled diet as a baseline for human studies: effects of nutrient intakes on blood pressure and on constituents of blood and urine.

This study demonstrates that a three-week stabilization period, in which all subjects eat an identical diet, produced a more uniform but different baseline of metabolic parameters than the subject's self-selected or "habitual" diets. Subjects required more food energy to maintain initial body weights during the stabilization period than when they ate their reported self-selected diets; average intakes of almost all nutrients were higher from the stabilization than from the self-selected diet. The switch to the stabilization diet produced small but significant reductions in blood pressure, in some serum enzymes, urine volume, and sodium; and statistically significant increases in serum LDL cholesterol, potassium, aldosterone, protein, albumin, phosphorus, BUN, and in urine potassium. The findings indicate that results must be interpreted with caution from studies in which the baseline for measuring metabolic variables is established by feeding subjects a standardized diet that differed markedly from their regular, self-selected diets.

Adult↗
PubMed1986

Vitamin E in foods from high and low linoleic acid diets.

As part of a human diet study, vitamin E activity was estimated in foods used in seven daily menus. Each menu was designed to contain 35% fat calories with either 10 or 30 gm/day of linoleic acid (18:2) and 500 mg/day of cholesterol. To estimate vitamin E activity, each food used in the menus was analyzed for alpha and gamma tocopherol content by high-pressure liquid chromatography with fluorescence detection. This article reports the alpha and gamma tocopherol contents of those foods, tocopherol contributions from each food in one sample 2,400-kcal menu, and the mean daily vitamin E activity (milligram alpha tocopherol equivalents) of all seven menus at five caloric levels. Major sources of alpha tocopherol (greater than 10% of the RDA) common to both diets (10 and 30 gm linoleic acid) were olive oil and a few fruits and vegetables. Additional major sources in the 30-gm linoleic acid diets were polyunsaturated fatty acid (PUFA) vegetable oils and margarine. Contrary to a common assumption, increasing the level of PUFA in the menus did not necessarily result in higher milligram equivalents of alpha tocopherol because soybean oil, with a tocopherol composition that is predominantly gamma tocopherol, was the major source of linoleic acid in the diets. Thus, vitamin E activity was not necessarily increased when soybean oil was substituted for a less saturated fat such as olive oil, which has mostly alpha tocopherol.

Chromatography, High Pressure Liquid↗
PubMed1985

Moderate changes in linoleate intake do not influence the systemic production of E prostaglandins.

A pilot study was undertaken to determine if moderate changes in linoleate (18:2 omega 6) intake would modulate the prostaglandin E turnover concurrently with, or independently of, changes in the plasma prostaglandin (PG) precursor levels. Four adult male volunteers in good health were fed two controlled diets containing 35% of energy from fat, with either 10 (diet L) or 30 g (diet H) linoleate/day, 30 to 50 g saturated fatty acids/day, and the balance mainly monounsaturated fatty acids. All four subjects were consuming sufficient amounts of polyunsaturates before the study. Protein (13-14%) and carbohydrate (51-53%) contribution to total caloric intake was kept constant. The menu cycle was 7 days, and all diets were calculated to provide adequate amounts of nutrients known to be required by man when data were available. Plasma fatty acids were determined by gas-liquid chromatography, and the turnover of E prostaglandins was assessed by measuring the urinary output of the major metabolite of PGE1 + PGE2 (PGE-M). Whereas we found a clear correlation between 18:2 omega 6 intake and 18:2 omega 6 concentrations in the neutral lipid (P = 0.007) and phosphoglyceride (P = 0.012) fractions of plasma, arachidonate (20:4 omega 6) concentrations in those same plasma fractions did not respond significantly to changes in linoleate intake. Moreover, we could not detect an influence of moderate changes in dietary levels of 18:2 omega 6 on the systemic production of PGE as measured by the daily urinary output of PGE-M.

Adult↗
PubMed1984

Evaluation of long-term dietary intakes of adults consuming self-selected diets.

Mean daily intakes of calories and 19 nutrients were calculated for 13 males and 16 females, ages 20 to 53 yr, who kept daily diet records for 1 yr. Mean daily caloric and 19 selected nutrient intakes of the subjects met or exceeded the 1980 recommended dietary allowances except for iron and calcium for females. Males had higher intakes than females for all nutrients studied except crude fiber, vitamin A, and vitamin C. However, nutrient density values were comparable for both sexes, except that the females had higher nutrient density values for vitamin A than did the males. The younger subjects had higher intakes of calories and saturated fat than the older ones. The younger males had higher intakes of total fat, saturated fat, and oleic acid than the older males. The consistency of reporting food intakes examined by applying a systematic sampling method designed for this study did not vary considerably when diet records kept over a long period of time were evaluated by four methods.

Adult↗
PubMed1984

Effect of making duplicate food collections on nutrient intakes calculated from diet records.

In a 1-yr study in which food intakes were recorded daily, subjects were asked to make duplicate food collections for 1 wk during each of the four seasons. Mean calculated energy intake of the 29 subjects was 12.9% less during the food collection periods than the mean for the entire year (which included collection periods). There were also significant reductions in the reported intake of all nutrients during the collection periods. Protein, vitamin A, saturated fat, and cholesterol intakes were decreased to the greatest extent. The actual decrease in energy intake was greater for the males than for the females, but the percentage was the same (12.9%). The younger group of subjects (less than or equal to 35) decreased energy intake 16.8% and the older group (greater than 35) 8.8%. Comparison of intakes during collection periods with intakes the week before and the week after showed that 28 of the 29 subjects decreased their energy intake from 1.1 to 32.3%. These data suggest that intakes of subjects during food collection periods do not represent their habitual levels of intake reported throughout the year.

Adult↗
PubMed1984

Calcium release and sarcoplasmic reticulum membrane potential in frog skeletal muscle fibres.

Single twitch fibres were dissected from frog muscle, stretched to a sarcomere spacing greater than or equal to 3.9 micron, then mounted for optical recording. The experiments were carried out at 15-17 degrees C. In some cases D2O Ringer solution was used instead of H2O Ringer solution to reduce movement and any related optical artifacts. Following action potential stimulation, both the amplitude and time course of the change in intrinsic retardation (Baylor & Oetliker's second component, 1975) were found to be approximately independent of wavelength between 480 and 750 nm (D2O Ringer solution). Fibres were injected with the Ca2+-sensitive dye Arsenazo III so that changes in myoplasmic free [Ca2+] could be estimated by measuring changes in dye-related absorbance at 660 nm. The time course of free [Ca2+] was compared with the time course of two other optical signals which have been previously suggested to monitor s.r. (sarcoplasmic reticulum) membrane potential, intrinsic retardation and Nile Blue A fluorescence (Bezanilla & Horowicz, 1975). In D2O Ringer solution the retardation time course was closely similar to that of free [Ca2+] whereas the fluorescence time course was considerably slower. Thus, it is possible that either the retardation signal or Nile Blue A fluorescence (or both) monitors free [Ca2+] rather than s.r. potential. If so, the underlying mechanism which senses Ca2+ must do so very rapidly in the case of retardation and with a delay in the case of Nile Blue A. Changes in Nile Blue A fluorescence were measured in a voltage-clamped fibre (H2O Ringer solution). Only small changes were observed during hyperpolarization or small depolarization whereas relatively large changes were observed near mechanical threshold. These increased e-fold in magnitude every 4-5 mV. This steep voltage dependence, similar to that already shown for intrinsic retardation and [Ca2+], provides additional evidence that Nile Blue A fluorescence monitors a step in excitation-contraction coupling. Theoretical waveforms of s.r. membrane potential were computed using a typical waveform of s.r. Ca2+ release (from Baylor, Chandler & Marshall, 1983) under the assumption that Ca2+ crosses the s.r. membrane as electrical current. Voltage waveforms were calculated using several combinations of electrical parameters for the s.r. membrane. Only certain combinations gave theoretical potential changes similar to the intrinsic retardation or Nile Blue A fluorescence signal.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Ionic currents and charge movements in organ-cultured rat skeletal muscle.

The middle of the fibre voltage-clamp technique was used to measure ionic currents and non-linear charge movements in intact, organ-cultured (in vitro denervated) mammalian fast-twitch (rat extensor digitorum longus) muscle fibres. Muscle fibres organ cultured for 4 days can be used as electrophysiological and morphological models for muscles in vivo denervated for the same length of time. Sodium currents in organ-cultured muscle fibres are similar to innervated fibres except that in the temperature range 0-20 degrees C (a) in the steady state, the voltage distribution of inactivation in cultured fibres is shifted negatively some 20 mV; (b) at the same temperature and membrane potential, the time constant of inactivation in cultured fibres is about twice that of innervated fibres. Potassium currents in innervated and cultured fibres at 15 degrees C can be fitted with the Hodgkin-Huxley n variable raised to the second power. Despite the large range we would estimate that the maximum value of the steady-state potassium conductance of cultured fibres is about one-half that of innervated fibres. The estimated maximum amount of charge moved in cultured fibre is about one-third that in innervated fibres. Compared to innervated fibres, culturing doubles the kinetics of the decay phase of charge movement. The possibility of a negative shift of the voltage distribution of charge movements in cultured fibres is discussed.

Action Potentials↗
PubMed1984

A comparative study of the transverse tubular system of the rat extensor digitorum longus and soleus muscles.

An ultrastructural comparison was made between the transverse tubular systems of the extensor digitorum longus (fast twitch) and the soleus (slow twitch) muscles in the rat. Quantitative measurements were made of the volume fraction, surface to volume ratio, surface density and foot density of the T system membrane. The values for the volume fraction and surface density were approximately 50% higher in the fast twitch (extensor digitorum longus) than the slow twitch (soleus) muscle. The dimensions of the tubules and hence the surface to volume ratio was the same in the two muscles. There was no difference in the spacing of the feet, so the reported three to fivefold difference in charge movement cannot be associated with a difference in foot density. Material lying within the lumen of the T tubules was observed in the majority of tubule profiles. This material, not hitherto described, was particulate or, more commonly, laminar in form.

Animals↗
PubMed1983

Sarcoplasmic reticulum calcium release in frog skeletal muscle fibres estimated from Arsenazo III calcium transients.

Single twitch fibres, dissected from frog muscle, were injected with the metallochromic dye Arsenazo III. Changes in dye-related absorbance measured at 650 or 660 nm were used to estimate the time course of myoplasmic free [Ca2+] following either action potential stimulation or voltage-clamp depolarization (temperature, 15-17 degrees C). The amplitude of the Ca2+ transient decreased when fibres were stretched to sarcomere spacings approaching 4 microns. The effect appeared to be less marked in H2O Ringer than in D2O Ringer, where a reduction of about 40% was observed in going from 3.0 microns to 3.7-3.9 microns. In fibres heavily injected with dye (1.5-2.2 mM-dye) at least 0.1 mM-Ca2+ was complexed with Arsenazo III following a single action potential, implying that at least 0.1 mM-Ca2+ was released from the sarcoplasmic reticulum (s.r.) into the myoplasm. Computer simulations were carried out to estimate the flux of Ca2+ between the s.r. and myoplasm (in fibres containing no more that 0.8 mM-dye). The amounts and time courses of Ca2+ bound to the Ca2+-regulatory sites on troponin and to the Ca2+, Mg2+ sites on parvalbumin were estimated from the free [Ca2+] wave form and the law of mass action. In the computations the total myoplasmic [Ca2+] was taken as the total amount of Ca2+ existing either as free ion or as ion complexed with dye, troponin or parvalbumin. The time derivative of total myoplasmic [Ca2+] was used as an estimate of net Ca2+ flux (release minus uptake) from the s.r. into myoplasm. Rate constants for formation of cation: receptor complex were taken from published values. For the Ca2+-regulatory sites on troponin, three sets of rate constants, corresponding to two values of dissociation constant (0.2 and 2 microM) were used. Each set of three simulations was carried out both with and without parvalbumin. The simulations show that following action potential stimulation, 0.2-0.3 mM-Ca2+ enters the myoplasm from the s.r. The wave form of s.r. Ca2+ release is early and brief compared with the wave form of free [Ca2+]. Neither the selection of troponin rate constants nor the inclusion of parvalbumin has much effect on the shape of the release wave form; the main effect of varying these parameters is to change the magnitude. After the initial, rapid phase of Ca2+ release from the s.r. there is a longer, maintained period of Ca2+ uptake.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1982

Optical measurements of intracellular pH and magnesium in frog skeletal muscle fibres.

1. Single twitch fibres were isolated from frog muscle, then mounted in a chamber which was positioned on an optical bench. The fibres were immobilized by high stretch (sarcomere spacing 3.9-4.3 mum) and by placement on a pedestal. Their optical properties were determined by illuminating a 35-65 mum diameter spot with quasimonochromatic light of intensity I(0) and measuring the intensity I of the transmitted light. Since the main purpose of the experiments was to draw inferences from the absorbance spectra of different indicator dyes injected into the fibres, all results were expressed in terms of absorbance A calculated from the equation [Formula: see text]. Changes in absorbance DeltaA were calculated from the differential form of the equation [Formula: see text].2. The absorbance of a normal, non-injected fibre was, on average, equal to 0.03 at 570 nm and varied approximately inversely with wavelength between 450 and 750 nm.3. The earliest change in absorbance following an action potential was a small, transient increase which was followed by a larger decrease. The decrease in fibre absorbance varied from 0.5 x 10(-4) to 3 x 10(-4) units.4. Resting myoplasmic pH was determined by comparing the absorbance spectrum from fibres injected with Phenol Red with that obtained from calibrating solutions in cuvettes. The muscle measurements were corrected for the intrinsic absorbance of fibre without dye. The average value of pH in two fibres was 6.9. The change in absorbance following an action potential in these highly stretched fibres was small. In one experiment the change, if due to pH alone, corresponded to an increase in pH of 0.004 peak and 0.002 maintained (relative to a resting level of 6.9). The maintained signal can be satisfactorily explained by the known amount of phosphocreatine hydrolysis.5. Estimates of myoplasmic free [Mg(2+)] were made using three metallochromic indicator dyes. A different estimate was obtained with each dye as indicated below. Since these dyes are sensitive to pH, as well as [Mg(2+)], the estimate depends on the assumed value of intracellular pH. [List: see text] This variability probably means that at least two, and possibly all three dyes behave differently inside muscle fibres than they do in calibrating solutions. The most likely explanation is that dye, once injected, can bind to cellular contents and that this alters its properties.6. Changes in absorbance of fibres injected with Arsenazo I, a dye three times more sensitive to Mg(2+) than to Ca(2+), were used to determine whether changes in free [Mg(2+)] occur following an action potential. The observed changes were small and could be due to a small increase in pH, of the magnitude measured with Phenol Red, and/or free [Mg(2+)]. In terms of a change in free [Mg(2+)], the results set an upper limit of 2%.7. The conclusion from the action potential experiments is that neither intracellular pH nor free [Mg(2+)] changes appreciably in highly stretched fibres. Changes in these two quantities can therefore be neglected in analysing the relatively large 650-660 nm Ca(2+) signal in fibres injected with the Ca(2+) (but also pH and Mg(2+)) sensitive indicator dye Arsenazo III.

Action Potentials↗
PubMed1982

Use of metallochromic dyes to measure changes in myoplasmic calcium during activity in frog skeletal muscle fibres.

1. Changes in transmission of quasi-monochromatic light were measured in singly dissected, dye-injected twitch fibres following a single propagated action potential. The records, after correction for the intrinsic transmission signal, indicate changes in dye-related absorbance, DeltaA. This paper describes the different components of dye-related signals in fibres injected with either Arsenazo III, Antipyrylazo III or Dichlorophosphonazo III.2. Fibres injected with Arsenazo III can show two kinds of changes in dye-related absorbance, an early isotropic change and a later dichroic change. The isotropic signal, which is the main subject of this paper, is transient in nature; it starts to develop before tension, reaches a peak in about 10 msec and is nearly over by 0.1 sec (16 degrees C). This signal is largest at 650-660 nm and measurements in this range indicate that the peak DeltaA varies approximately linearly with dye concentration between 0.2 and 0.7 mM. The wavelength dependence of the peak amplitude can be qualitatively fitted by the Ca(2+)-difference spectrum determined from cuvette calibration measurements. There may be a small maintained (0.4-0.5 sec) absorbance change of a few percent of the peak value at 650-660 nm, possibly reflecting a maintained increase in myoplasmic pH or free [Mg(2+)].3. In a fibre injected with approximately 0.5 mM-Antipyrylazo III, there were two kinds of dye-related absorbance signals, both of which were isotropic. There was no signal that was obviously dichroic. The earlier signal was similar in time course to the early isotropic Ca(2+) signal which was measured with Arsenazo III, and its magnitude followed the wavelength dependence of the Ca(2+)-difference spectrum determined from cuvette calibration measurements. By contrast, the wavelength dependence of the later absorbance change was similar to either the H(+) or Mg(2+)-difference spectrum. The direction of this late signal (0.2 sec after stimulus) would correspond to an increase in either myoplasmic pH or free [Mg(2+)]. Records of the absorbance change at all wavelengths can be fitted by a linear combination of the Ca(2+) waveform and the H(+)/Mg(2+) waveform.4. Fibres injected with Dichlorophosphonazo III showed three dye-related absorbance changes. There was an early isotropic signal, a later dichroic signal and a second isotropic signal. The wavelength dependence of the first part of the early signal is similar to the Ca(2+)-difference spectrum whereas the wavelength dependence of the second isotropic signal is similar to the H(+)- or Mg(2+)-difference spectrum. As was the case with Arsenazo III and Antipyrylazo III, the direction of the second signal at late times would correspond to an increase in either pH or free [Mg(2+)]. Replacing H(2)O with D(2)O resulted in a marked diminution of the dichroic signal. In D(2)O, linear combinations of two basic isotropic waveforms were sufficient to account for the absorbance changes measured at all wavelengths.5. With all three metallochromic dyes, the time course of the early isotropic signal is similar to that of the second component of the intrinsic birefringence signal, at least to time of peak. On the assumption that this birefringence signal bears a unique temporal relationship to the myoplasmic free [Ca(2+)] waveform, at least to time of peak, the similarity suggests that all three dyes track free [Ca(2+)] with similar speed.6. The conclusion from the experiments is that there are, in general, two dye-related isotropic absorbance signals seen with Arsenazo III, Antipyrylazo III and Dichlorophosphonazo III. One has an early, transient time course and appears to be due to the formation of Ca(2+): dye complex in response to a transient increase in myoplasmic free [Ca(2+)]. The other signal persists after the free [Ca(2+)] transient has decayed. This appears to be due to a change in H(+): dye or Mg(2+): dye complex, such as would occur if there were a small maintained increase in myoplasmic pH or free [Mg(2+)].

Action Potentials↗
PubMed1982

Dichroic components of Arsenazo III and dichlorophosphonazo III signals in skeletal muscle fibres.

1. Absorbance changes were measured following stimulation of single muscle fibres injected with the metallochromic indicator dye Arsenazo III. Two dye-related signals can be clearly resolved: (1) an early, transient isotropic signal that appears to be due to the formation of Ca(2+):dye complex and (2) a slower, transient signal that is ;dichroic' in nature. The dichroic signal is obtained by taking the difference between absorbance changes measured with light plane polarized along the fibre axis (0 degrees light) and at right angles to the axis (90 degrees light).2. The time course of the dichroic signal is the same at all wavelengths employed, suggesting that a single underlying process is involved. The wavelength dependence of the magnitude of the signal is similar to that obtained for dye absorbance in a resting fibre.3. At 570 nm, near the isosbestic wavelength for changes in H(+):dye, Mg(2+):dye and Ca(2+):dye, the dichroic signal is near maximal. The absorbance change with 0 degrees light is positive and is about twice as large as the change with 90 degrees light, which is negative. This finding is consistent with the idea that the dichroic signal arises from dye molecules which change their orientation in the radially symmetric muscle fibre. The direction of the change is for the dye's transition moment to become more aligned with the fibre axis during activity.4. During a train of ten action potentials the (isotropic) Ca(2+) transient increases in magnitude three-fold, whereas the dichroic waveform reaches a plateau value only 30-40% larger than the single twitch value.5. Replacing H(2)O in Ringers with D(2)O causes a slight reduction in the Ca(2+) signal, reduces the dichroic signal to 0.4 times normal, and reduces tension to 0.1 times normal. Qualitatively similar reductions were found to accompany an increase in osmolality of H(2)O Ringer from 1 x to 2.5 x normal.6. Dichroic signals are also observed in fibres injected with Dichlorophosphonazo III. These are similar in many respects to the Arsenazo III dichroic signals.7. With Arsenazo III, the dichroic signal probably arises from a reorientation of some dye molecules which are bound to one of the oriented structures in muscle. The reorientation lags the Ca(2+) transient and may be due to a change which occurs in the oriented structure itself. Using this idea, the Arsenazo III dichroic signal can be fitted by assuming that Ca(2+) ions bind to receptor sites and that this binding induces the required change in the oriented structure. The analysis indicates that the hypothetical receptors have a dissociation constant for Ca(2+) equal to 0.1-1 times the peak value of myoplasmic free [Ca(2+)] during a twitch and an ;off' rate constant equal to 10-30 sec(-1) at 15 degrees C.

Action Potentials↗
PubMed1982

Calculates vs. analyzed composition of four modified fat diets. Formulated to study effects in human subjects of kind and amount of dietary fat.

Four diets, varying in kind and amount of fat, were calculated to meet the needs of adult men. Commonly available U.S.A. food were used. Fourteen days of menus, each with five caloric levels varying from 2,400 to 4,000 kcal, were calculated. Chemical analyses of composites were carried out to determine proximate composition, food energy, selected vitamins and minerals, sugars, fatty acids, and sterols. The diets were used in a controlled study of the effects of fat level and P:S on blood pressure, blood lipids, platelet aggregation, and other variables. In general, good agreement was found between calculated and analyzed nutrient contents. However, analyzed values for fiber, iron, cholesterol, and vitamin C showed larger than desirable differences from calculated values.

Cholesterol, Dietary↗