Ultrastructural changes in the mitochondria of brown adipose cells during the hibernation cycle of Citellus lateralis

Summary The mitochondrial structure in the brown adipose cells of the golden mantled squirrel, Citellus lateralis, was examined throughout the year in biopsy samples. The mitochondria showed remarkable and apparently reversible changes in size and internal structure related to the physiologic activity of the animal. In the active animal the size of the largest mitochondria was 2.4 m × 1.5 m; during hibernation it increased to 7 m × 2.5 m; and during arousal it reached 11.2m × 5.3 m. The cristae of the mitochondria in the brown adipose cells of the animals in hibernation phase formed loops, whorls and mesh-like interconnections. During the arousal phase they underwent further configurational changes. The most remarkable structure was associated with mitochondria of most unusual proportions which by dissolution gave rise to a new generation. This was a common finding during arousal but did not occur in any other phase of the hibernation cycle. The new mitochondria were virtually indistinguishable from those of brown adipose cells of any active animal.Supported by a grant from the Medical Research Council of CanadaThe author is grateful to colleagues, Dr. G. Dempster and Dr. W.A. Spencer, for many valuable suggestions in the course of the work     

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.     

Inner mitochondrial membrane anion channel is present in brown adipocytes but is not identical with the uncoupling protein

Summary Vesicles of inner mitochondrial membrane, mitoplasts, from rat brown adipose tissue were prepared by osmotic swelling and studied using the patch-clamp technique. Current events of a 107.8±8.7 pS (n=16, 21°C) channel were recorded in the mitoplast-attached mode. This channel was selective for anions and its kinetics resembled those of channels previously found in liver and heart mitochondria of mouse and ox. In whole-mitoplast mode each of five purine nucleotides (20 m) blocked the channel. This is the first demonstration of pharmacological blockade of this type of channel. Although a similar anion channel in mouse and ox mitochondria was suggested to be the uncoupling protein (UCP) associated with nonshivering thermogenesis, we present several arguments against this possibility. Thus we describe a high-conductance, purine-nucleotide-binding, anion selective mitochondrial channel, that is not the UCP.     

Postnatal changes in fatty acids composition of brown adipose tissue

It has been demonstrated that thermogenic activity of brown adipose tissue (BAT) is higher during the early postnatal period, decreasing towards a low adult level. The present study examined postnatal changes in the lipid composition of BAT. BAT from pre-weaning rats at 4 and 14 days old showed the following differences in lipid composition compared to that from adults of 12 weeks old. (i) Relative weight of interscapular BAT to body weight was markedly greater. (ii) BAT-triglyceride (TG) level was lower, while BAT-phospholipid (PL)level was higher. (iii) In TG fatty acids (FA) polyunsaturated fatty acids (PU; mol %), arachidonate index (AI), unsaturation index (UI) and PU/saturated FA (SA) were higher; rare FA such as eicosadienoate, bishomo--linolenic acid and lignoceric acid in mol % were also higher. (iv) In PL-FA monounsaturated FA (MU) in mol % was lower; PU mol %, AI and UI were higher. These features in BAT of pre-weaning rats resembled those in the cold-acclimated adults, suggesting a close relationship of the PL-FA profile to high activity of BAT.     

Continuous flow microcalorimetric measurement of heat production in white adipose tissue from obese (ob/ob) mice and their lean littermates

Heat production, free fatty acid and glycerol release from white adipose tissue fat pads from obese (ob/ob) mice and their lean littermates are determined. Heat production was significantly lower in obese mice compared to lean mice when expressed on wet weight basis but not when expressed on DNA basis. Noradrenaline significantly increased the heat production in fat pads from both groups of animals. However, the increase in heat production due to noradrenaline addition in fat pads from lean mice was significantly higher than in fat pads from obese mice. The release of free fatty acids and glycerol before incubation with noradrenaline was similar from fat pads from both groups of animals. Addition of noradrenaline to the fat pads increased the release of free fatty acids and glycerol in both groups of animals, but the increase was significantly larger from fat pads from lean mice. In the absence of noradrenaline the free fatty acid/glycerol ratio (mol/mol) in the effluent was 7.9:1 and 4.8:1 for lean mice and obese mice, respectively. In the presence of noradrenaline the ratio decreased to 3:1 for both groups of animals.     

Cationic responses of organs and haemolymph of Biomphalaria pfeifferi (Krauss), Biomphalaria glabrata (Say) and Helisoma trivolvis (Say) (Gastropoda: Planorbirdae) to cationic alterations of the medium

The cationic responses of haemolymph, mantle collar, headfoot, gut + digestive diverticulum and ovotestis + albumin gland of three planorbids to cationic changes in the media are explored. Body organs exhibited cationic homeostasis, although attained with difficulty under very low Ca : Mg and Ca : Na ratios. Haemolymph imbalances were obtained at very low calcium concentrations and at very low Ca : Mg and Ca : Na ratios in the medium; this may be linked to competition for Ca²⁺ uptake sites in the epithelium by Mg²⁺ and possibly Na⁺ ions.Fecundity and shell growth in relation to calcium concentrations and to Ca : Mg and Ca : Na ratios are examined.Normal internal cationic levels, under optimal conditions, were obtained for each species. Significant interspecific differences for haemolymph sodium were found; magnesium levels were slightly higher in Biomphalaria spp. than in Helisoma trivolvis; potassium levels were all similar. Amounts of tissue calcium decreased as follows: Mantle collar head-foot ovotestis + albumin gland-gut + diverticulum. Tissue magnesium levels in the gut were low. H. trivolvis had highest tissue calcium and sodium; B. glabrata had highest tissue potassium.     

Effect of temperature on isotonic twitch of white muscle and predicted maximum swimming speeds of skipjack tuna,Katsuwonus pelamis

Synopsis Latent period, rise time, contraction time, and half relaxation time from isotonic contractions of isolated white muscle samples from skipjack tuna, Katsuwonus pelamis, were determined at 20°, 27°, and 34° C. These parameters were found to be inversely proportional to temperature (Q₁₀ = 1.47, 1.67, 1.62, and 1.72, respectively). The data show that contraction time and the effect of temperature on contraction time of skipjack tuna white muscle are not unique when compared to other equal-sized teleosts. Based on contraction time, maximum swimming speeds at each muscle temperature were calculated and found not significantly to exceed the maximum speeds of other equal-sized teleosts, when comparisons are made at the same white muscle temperatures     

The occurrence of the second moult of Ascaris lumbricoides and Ascaris suum

Maung M. 1978. The occurrence of the second moult of Ascaris lumbricoides and Ascaris suum. International Journal for Parasitology 8: 371–378. Eggs of Ascaris lumbricoides and A. suum were cultured at 28°C and observed daily. Larvae were released by pressure, by artificial hatching with CO₂, and by natural hatching after infection of laboratory mice. The early stages of development in the egg were observed to comprise two moults, one occurring immediately after the other. Both moults were initiated within the egg, but the time of completion of the second moult varied considerably, and in some instances was not completed until the larvae reached the liver of experimentally infected animals.     

Metabolic effects of glucose deprivation and of various sugars in normal and transformed fibrobalst cell lines.

The sugar composition of the growth medium influenced the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio, pyruvate and lactate production, and ATP levels in both normal and transformed fibroblast cell lines growing in tissue culture. Removal of glucose led to a rapid three- to fourfold rise in the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio, followed by a slower decline in the content of ATP. However, there was no change in the adenylate energy charge [$\text{(}\text{ATP}\text{+}\text{1}\text{2}\text{ADP}\text{)/(}\text{ATP + ADP + AMP}\text{)}$] over a 2-h period. The $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio was restored to the original level within 10 s of glucose readdition. The $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ratios in cell lines growing on galactose were as high as for those incubated without sugars; growth on mannose or fructose produced intermediate ratios. There was an inverse relationship between the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio and pyruvate-lactate production for glucose, fructose and galactose. Thus, all cell lines had a high production of pyruvate and lactate but a low $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio when grown on glucose. In contrast, when galactose served as the sugar source, acid production was low, while the ratio was high. All cell lines had comparable hexokinase activity, and glucose was the best substrate, mannose intermediate and fructose poorest. Hexokinase activity did not correlate with the relative degree of utilization of the sugars. These results suggest that the sugar composition of the growth medium affects the metabolic pattern of a cell line, including the $\text{NAD}{}^{\mathrm{+}}\text{NADH}$ ratio, the ATP content and the production of pyruvate and lactate.