Succinic Dehydrogenase Distribution in the Pectoralis Muscle of Several East African Birds

The distribution of succinic dehydrogenase activity was investigated in the pectoralis muscle of thirteen East African birds, representing five Orders. It was found that the pectoralis muscle of the most primitive birds studied (Galliformes) contained all “white” muscle fibres whereas the more advanced birds (Passeriformes) had all “red” muscle fibres. Intermediate Orders had mostly a mixture of red and white muscle fibres. There also appeared to be a direct relationship between body size and average muscle fibre size. However, it was concluded that the most important factor in relation to the muscle structure is the bird's mode of flight. The relationship with the degree of evolution and body size only held true in so far as the birds which had developed the facility for sustained flight, by increasing their red muscle fibre content, were also smaller in size and constituted the more “evolved” Orders of birds. In support of this it was noted that migratory birds (i.e. engaging in sustained flight) from more primitive Orders also had a high red muscle fibre content in their pectoralis muscles.     

The enzyme "aldehyde oxidase" is an iminium oxidase. Reaction with nicotine delta 1'(5') iminium ion.

The second of the two reaction steps involved in the metabolic transformation of (?)-nicotine to (?)-cotinine $\text{(}\text{3}\text{) (}\text{i.}\text{e.}$, the oxidation of the intermediate $\text{2}\text{)}$ is mediated mainly, if not solely, by the enzyme aldehyde oxidase (EC 1.2.3.1). Of the molecular species that constitute $\text{2}$, nicotine Δ^1′(5′) iminium ion $\text{(}\text{2a}\text{)}$ appears to serve as the substrate. The enzyme has a strong affinity for $\text{2a}$, as shown in a study on the inhibition of the oxidation of 3-(aminocarbonyl)-1-methylpyridinium chloride. This study gave a value of K_i = 6 μM; K_m = 2 μM (pH 7.4). Mainly in view of this finding, “iminium oxidase” seems to be a more adequate name than “aldehyde oxidase” for this enzyme.     

Carbohydrate structure and serological behaviour of "antifreeze" glycoproteins from an Antarctic fish.

The carbohydrate moiety of the “antifreeze” glycoprotein from $\text{Trematomus borchgrevinki}$ was found to be β-D-galactosyl 1–3 N-acetyl galactosamine by gasliquid chromatography. The glycoprotein inhibited anti-T antibody from human serum and $\text{Arachis hypogoea}$ lectin, but was inactive against $\text{Vicia graminea}$. Native “antifreeze” glycoprotein did not inhibit the agglutinins from $\text{Helix pomatia}$ or $\text{Cepaea hortensis}$, although after Smith degradation showed a strong inhibition towards them. Inhibition of the latter agglutinin demonstrates the carbohydrate-protein linkage to be α-linked. The presence of the Thomsen-Friedenreich antigen (T-antigen) on the “antifreeze” glycoprotein and its relation to tumour cell surfaces is briefly discussed.     

Modification of hepatic microsomal oxidative drug metabolism in rats by the opiate maintenance drugs acetylmethadol, propoxyphene, and methadone.

The formation of cytochrome P-450 “metabolic intermediate” complexes $\text{in}$$\text{vivo}$ occurred with acetylmethadol and propoxyphene, but not methadone in both naive and phenobarbital-induced animals. The $\text{in}$$\text{vivo}$ formation correlated with the relative ability of these three compounds to form metabolic intermediate complexes and inhibit mixed-function oxidation reactions $\text{in vitro}$.     

Glucocorticoid tight binding in rat liver and thymus particles

Glucocorticoid binding to certain cell particles of rat liver and thymus following treatments $\text{in vivo}$ and $\text{in vitro}$ consists in part of a very “tight binding” that resists hot and cold perchloric acid extractions. This binding is found in thymus nuclei and in liver cytoplasmic particles, but not in liver nuclei nor in thymus mitochondria or microsomes. The existence of “tight binding” coincides with the ability of the same particles to bind free corticoid directly in incubations $\text{in vitro}$. The difference in the cellular location of this binding suggests that different methods of glucocorticoid activation exist in the anabolic target tissue, liver, and the catabolic target tissue, rat thymus.     

A dielectric theory of "multi-stratified shell" model with its application to a lymphoma cell

A theory of complex dielectric constant ($\text{ε}{}^1$) for the suspension of “multi-stratified” spherical particles is presented. Based on Maxwell's theory of interfacial polarization, we derive a general expression which correlates $\text{ε}{}^1$ with the electrical and geometrical parameters of each stratum. It can be shown that such a “multi-stratified” system in general should give rise to multiple dielectric dispersions, the number of which corresponds to the number of interfaces lying between the successive shell phases. The conditions for a full number of different “unit” dispersions to occur are also discussed. As an example, a special case of the “double-shell” model consisting of a spherical core and three layers of concentric phases is solved numerically by using a set of parameter values pertinent to a lymphoma cell. In light of the characteristic behavior of $\text{ε}{}^1$ thus revealed, we propose a scheme of procedure that applies to the determination of electrical parameters associated with the specific “double-shell” model.     

The role of the synaptic vesicles in transmission at the insect nerve-muscle junction

The ultrastructure of nerve-muscle synapses on red and white fibres of locust ($\text{Schistocerca}$$\text{gregaria}$) retractor unguis muscle fibres was examined before and after stimulation. At a stimulation frequency of 15Hz, the synapses on the white fibres fatigued completely; those on the red fibres also fatigued, but during prolonged stimulation they showed intermittent periods of recovery. Synaptic vesicles at both types of fatigued synapses were reduced in volume compared with controls and at fatigued synapses on white fibres the vesicles had irregular outlines. Aggregation of vesicles were observed at fatigued synapses on red fibres and the synaptic cleft width at these synapses was less than at control synapses on red fibres. These results are discussed in the light of the vesicle hypothesis for synaptic transmission.     

Harmaline distribution in single muscle fibres and the inhibition of sodium efflux

Harmaline, a known inhibitor of the ($\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ in cell membranes, inhibited 50% of the ²²Na efflux from barnacle muscle fibres at an extracellular concentration of 2.4 mM. Injected harmaline inhibited 50% of the efflux at an estimated intracellular concentration of about $\text{8}\text{mM}\text{·}\text{kg}{}^{\mathrm{?1}}$, assuming complete equilibration with no binding. Total fibre harmaline was measured in separate fibres by ultraviolet spectrophotometry. Fibres in 3 mM harmaline saline accumulated harmaline with a half-time of 17 min and a final total fibre concentration of $\text{6–12}\text{mM}\text{·}\text{kg}{}^{\mathrm{?1}}$. In harmaline-free saline this accumulated harmaline was lost exponentially with a half-time of 35 min; injected harmaline was lost exponentially from fibres with a half-time of 50 min. It is proposed that harmaline crosses the fibre membrane as the uncharged base and that its apparent accumulation against a concentration gradient is mainly due to intracellular binding with an additional contribution from a transmembrane pH gradient. It is concluded that, in fibres exposed to harmaline saline, the intracellular concentration can reach a sufficiently high value, as judged from the results of the injection experiments, to inhibit Na⁺ efflux at an interior-facing site on the fibre membrane. In contrast, harmaline appears to inhibit the Na⁺-dependent uptake of l-glutamate at an extracellular site.     

On the heterogeneity of capillaries of pigeon pectoralis muscle: a histoenzymatic and ultrastructural study

Synopsis Earlier studies had failed to show the presence of capillaries between the white fibres of pigeon pectoralis muscle. In this paper, data are reported for the first time documenting that these capillaries occur in both intra- and inter-fasicular areas of the muscle. Fresh frozen sections of pigeon pectoralis major muscle were incubated for alkaline ATPase reaction following pretreatment with different EDTA solutions (4.3 mM, pH 4.3). The results showed the existence of an inherent heterogeneity of capillaries. The capillaries of white fibres stained intensely for K^–/Mg^2–-EDTA or Mg²⁺-EDTA pre-incubated ATPase; the capillaries of red fibres stained poorly. Both white fibre and red fibre capillaries were examined ultrastructurally in the non-perfused pigeon pectoralis muscle. It is suggested that a possible correlation exists between the distinctive metabolic and mechanical characteristics of the Type II white, glycolytic, fast-twitch fast-fatigue muscle fibres and the high ATPase activity of their capillaries.     

The effect of short-term fasting on shivering thermogenesis in Japanese quail chicks (Coturnix coturnix japonica): indications for a significant role of diet-induced/growth related thermogenesis

(1) The effect of short-term fasting on metabolism and shivering thermogenesis was studied in 9-day-old Japanese quail. (2) After 31 h of fasting, heat production decreased 39% and body temperature over 2°C in the thermoneutral zone. The difference in heat production between control and fasting groups decreased with decreasing ambient temperature. (3) Despite the lower metabolic rate, the amplitudes of shivering EMGs were higher in fasted chicks, especially in pectoralis. This indicates that fasted quails used shivering to compensate the decrease in diet-induced/growth related thermogenesis. (4) In cold, conductance of control birds decreased simultaneously with increasing heat production while in fasted chicks, conductance decreased to its minimum before heat production was activated. (5) Japanese quail chicks adapt quickly to short-term fasting by decreasing metabolism but they maintain their ability to thermoregulate in cold. Diet-induced/growth related thermogenesis has a significant role in thermoregulation since it reduces the need of shivering thermogenesis.     

Comparative aspects of fibre types,areas, and capillary supply in the pectoralis muscle of some passerine birds with differing migratory behaviour

Summary Fibre types, fibre areas and capillary supply in the pectoralis muscle of fifteen passerines with four different patterns of migratory behaviour have been studied. The predominant fibre type was a fast-twitch oxidative-glycolytic which was the only fibre type present in all species, except in the robin and the blackbird where a fast fibre with intermediate oxidative capacity and a fast glycolytic fibre were also found. There was a significant difference in fibre areas between birds with different migratory strategies, with the long-distance migratory group having the smallest fibres. This also led to higher capillary densities, shorter diffusion distances and, consequently, more capillaries around the fibres relative to fibre area in this group. This indicates an adaptation in the morphology of the pectoralis muscle to differences in migration strategies. In the robin, the proportion of the intermediate fibre was significantly greater during the breeding season than during migration. Seasonal differences in fibre areas and capillary supply within a species were also seen, but no definite trends were detectable.Abbreviations CC capillary/fibre contacts - CCA mean number of capillaries in contact with a fibre relative to fibre cross-sectional area - MD mean diffusion length - CD capillary density - FG fast-twich glycolytic - FOG fast-twitch oxidative-glycolytic     

Light-break experiments and photoperiodic time measurement in the spider mite Tetranychus urticae

To explain photoperiodic induction of diapause in the spider mite Tetranychus urticae (Acarina: Tetranychidae) a theoretical model was developed, consisting of two components, viz. a “clock” and a photoperiodic “counter” mechanism. The clock executes photoperiodic time measurement according to hourglass kinetics; the counter accumulates the photoperiodic information contained in a number of successive $\text{light}\text{dark}$ cycles by adding up the number of “long” and “short” nights experienced by the developmental stages of the mites sensitive to the photoperiod. The influence of the circadian system on photoperiodic induction is interpreted as an inhibitory effect exerted on the expression of the photoperiodic response; this effect is encountered only in certain photoperiodic regimes, where the circadian system and the photoperiod are out of “resonance” with each other. This “hourglass timer oscillator counter model”, devised to give a theoretical explanation of photoperiodic time measurement, the summation of photoperiodic information, and the influence of the circadian system on photoperiodic induction, proved to be consistent with experimental results obtained with T. urticae in both symmetrical and asymmetrical “skeleton” photoperiods, the latter based on diel as well as non-diel $\text{light}\text{dark}$ cycles.     

Selective alterations in hepatic enzyme response after reduction of nuclear triiodothyronine receptor sites by partial hepatectomy and starvation.

Barley embryo 5S rRNA hybridizes efficiently with barley embryo 18S rRNA but not with 26S rRNA. Mouse sarcoma 5S rRNA also selectively hybridizes, to a smaller extent, with mouse sarcoma 18S rRNA. The barley embryo 5S–18S rRNA complex has a sharp melting profile and a “Tm” of $\text{ca}$. 59° in 0.1 $\text{M}$ NaCl. The mouse sarcoma 5S–18S rRNA complex has a broader transition breadth and a “Tm” of $\text{ca}$ 52°. The conditions used for hybridization lead to very specific reconstitution of the “natural” complex between 5.8S and 26S–28S rRNA since both the $\text{in}\text{vivo}\text{and}\text{in}\text{vitro}$ complexes between 5.8S and 26S–28S rRNA from barley embryos and mouse sarcoma have equally sharp melting profiles and a “Tm” of $\text{ca}$. 52° in 0.1 $\text{M}$ NaCl.     

A "Reverse burst" active site titration procedure for human carbonic anhydrase B.

Between pH 7 and pH 10.5, p-nitrophenyl $\text{p}$-sulfamyl benzoate (PNP-SAB) binds very strongly to human carbonic anhydrase B (dissociation constant on the order of 10^?9 M or less at pH 7.5), but is not hydrolyzed by the enzyme. Because the binding is essentially stoichiometric under readily accessible conditions, this ester may be used as an active site titrant, by measuring the rapid hydrolysis of excess unbound PNP-SAB catalyzed by an added nucleophile (“reverse burst”).     

Studies on the red oxidase (cytochrome o) of Azotobacter vinelandii

In an attempt to isolate and to study the electron transport system of $\text{Azotobacter vinelandii}$, we have isolated and purified a membrane-bound cytochrome $\text{o}$. The cytochrome $\text{o}$, purified as a detergent (Triton X-100) and hemoprotein complex, contained 1.6 nmoles heme per mg of protein. Cold-temperature spectrum showed that no other cytochrome was associated with the purified preparation, and electrophoresis revealed that only one type of hemoprotein was obtained. The purified cytochrome $\text{o}$ reacted with both carbon monoxide and cyanide readily. Only in the reduced form did it combine with carbon monoxide, whereas the oxidized form reacted with cyanide. An “oxygenated” form of the cytochrome $\text{o}$ was demonstrated to be spectrally distinguishable from both the oxidized and the reduced forms.     

Studies on the activity of brown adipose tissue in suckling,pre-obese, obob mice

The properties and activity of brown adipose tissue have been investigated in suckling, pre-obese, $\text{ob}\text{ob}$ mice in order to determine whether decreased thermogenesis in the tissue precedes the development of obesity in this mutant. At 14 days of age there was no difference between the $\text{ob}\text{ob}$ and normal animals in the total amount of interscapular brown adipose tissue, and the DNA content, protein content, and cytochrome oxidase activity of the tissue were similar in the two groups of mice. Respiration rates of brown adipose tissue mitochondria in the presence of albumin were, however, greater in the normal than the $\text{ob}\text{ob}$ animals, although after the addition of GDP to recouple the mitochondria there was no difference between the two groups. The mitochondrial membrane potential, measured with [³H]methyltriphenylphosphonium, was less affected by exogenous GDP in $\text{ob}\text{ob}$ mice than in normal animals. GDP binding to brown adipose tissue mitochondria, an index of the proton conductance pathway, was much greater in normal than in $\text{ob}\text{ob}$ mice at both 10 and 14 days of age; the decreased GDP binding in the mutant animals was found to result from a reduction in the number of binding sites. It is concluded that brown adipose tissue mitochondria of pre-obese $\text{ob}\text{ob}$ mice are more tightly coupled than those of normal siblings, and that the activity of the ‘thermogenic’ proton conductance pathway is lower in the mutant animals. A decrease in thermogenesis in brown adipose tissue is therefore an early event in the development of the $\text{ob}\text{ob}$ mouse and precedes the appearance of obesity.     

Control of pattern duplication in the retinotectal system of Xenopus. Induction of duplication in eye fragments by secondary cuts.

Following surgical ablation of the temporal (posterior) region of the eye-bud in stage 32 Xenopus frog embryos, the surviving nasal (anterior) fragment gradually rounds up to form a functional eye and orderly retinotectal map. Large nasal fragments ($\text{N}\text{-}\text{2}\text{3}$) assemble topographically normal maps, as does the majority of nasal “half-eye” fragments; small nasal fragments ($\text{N}\text{-}\text{1}\text{3}$), and a minority of nasal half-eye fragments, give a characteristic, mirror-symmetrical duplication map, similar (but not identical) to the “double-nasal” maps which develop when two nasal half-eyes are fused to form a frank NN double-eye. Ventral fragments and temporal fragments show similar size-dependent behavior, although their characteristic duplicate maps are topographically different from those of nasal fragments and more similar to the “double-ventral” and “double-temporal” maps of VV and TT recombinant eyes. Here we show that a simple surgical transection, applied either dorsally or ventrally to large nasal ($\text{N}\text{-}\text{2}\text{3}$) fragments so as to isolate a subregion of the tissue at the dorsum or venturm of the fragment, induces full or partial duplication of the nasal type in the majority of cases. The results refute the hypothesis that special properties at the eye-bud center, by their presence or absence in the fragment, control pattern duplication, and point instead toward interactions around the circumference of the eye-bud as a crucial parameter in determining positional information in the retina.     

Cloning of the replication origin from Drosophila virilis mitochondrial DNA.

Mitochondrial DNA from $\text{Drosophila}$ contains high “A+T”-rich region. Its DNA replication starts in the “A+T”-rich region and proceeds unidirectionally around the molecule. In order to determine precise location of the DNA replication origin and elucidate unique feature of its nucleotide sequence, the “A+T”-rich region of mitochondrial DNA from $\text{Drosophila}\text{virilis}$ has been cloned in $\text{Escherichia}\text{coli}$. The chimeric plasmid DNA containing the “A+T”-rich region stimulates $\text{in}\text{vitro}$ DNA replication system from $\text{Drosophila}\text{virilis}$ mitochondria about ten fold higher than the parental plasmid DNA, as does native mitochondrial DNA.     

Evidence for a glucosyl-enzyme intermediate in the beta-glucosidase-catalyzed hydrolysis of p-nitrophenyl-beta-D-glucoside

The reaction of almond β-glucosidase with $\text{p}$-nitrophenyl-β-$\text{D}$-glucoside has been investigated over the temperature range +25° to ?45° using 50% aqueous dimethyl sulfoxide (DMSO) as solvent. At temperatures below those at which turnover occurs a “burst” of $\text{p}$-nitrophenol proportional to the enzyme concentration is observed. Such a “burst” suggests the existence of a glucosyl-enzyme intermediate whose breakdown is rate-limiting, and provides a method for measuring the active-site normality. At pH 5.9, 25°, the presence of 50% DMSO causes an increase in K_m from 1.7×10^?3M (0%) to 1.7×10^?2M, whereas V_max is unchanged. The DMSO thus apparently acts as a competitive inhibitor with K_i = 0.7M. The Arrhenius plot for turnover is linear over the accessible temperature range with E_a = 23.0 ± 2.0 kcal/mole.