Chemical composition and alkaline phosphatase activity of nutrient-saturated and P-deficient cells of four marine dinoflagellates

Four marine dinoflagellates, Amphidinium carterae Hulburt, Ceratium tripos (O.F. Müll.) Nitzsch, Prorocentrum minimum (Pav.) J. Schiller, and Scrippsiella trochoidea (Stein) Loeblich III were grown as dilution cultures at 18°C, S = 29%. and 30 μE·m^?2·s^?1 at L:D = 14:10 h. In nutrient-saturated cultures, the growth rates (doubl·day^?1) ranged from 0.38 for Scrippsiella to 0.80 for Prorocentrum, and carbon content (pg·cell^?1) from 83 for Amphidinium to 6900 for Ceratium. The atomic $\text{N}\text{C}$ ratio was 0.13–0.15, but for Ceratium it was 0.088, because of its thick, cellulose theca. The atomic $\text{N}\text{P}$ ratio ranged from 12–13 for Ceratium and Scrippsiella to 15–17 for Prorocentrum and Amphidinium. Under P-deficient conditions (growth rate 39–70% of the maximum), cellular P decreased considerably, but so did N, so that the $\text{N}\text{P}$ ratio was only slightly affected. There was a concomitant increase in carbon content per cell of 1.2- to 1.7-fold. Alkaline phosphatase activity was virtually nil in nutrient-saturated cells, but was readily demonstrable in all species when P-deficient.     

Ecological investigations of the zooplankton community of Balsfjorden,northern Norway: Generation cycle,seasonal vertical distribution,and seasonal variations in body weight and carbon and nitrogen content of the copepod Metridia longa (Lubbock)

Metridia longa (Lubbock) has an annual life cycle in Balsfjorden (69°21'N:19°06'E) with spawning occurring from early to mid-May. Development through copepodite stages I-V takes place during summer. At the end of August copepodite stage V accounted for >80% of the population. Overwintering (October-March) was mainly performed by adults. At noon throughout the year copepodite stage V and adults were found within the bottom 30 m of the fjord. The majority of stage IV occurred within the bottom 80 m, while copepodite stages I-III were mainly concentrated within the surface 50 m. Body length, weight, carbon and nitrogen content, and $\text{C}\text{N}$ ratio were determined for copepodite stage V, adult males and females throughout the year. While body length was constant, weight and C and N content varied with season. Lowest $\text{C}\text{N}$ ratios (4–6) were found in copepodite stage V in July and in adults in late winter. Highest $\text{C}\text{N}$ ratios (16–20) were measured in adults from October through early winter. These results are discussed in relation to the life cycle of M. longa and the primary production cycle of the fjord. It is argued that M. longa overwinters in an active state compared with Calanus finmarchicus (Gunnerus) from the same locality.     

Oxygen equilibrium characteristics of hemoglobins of baboons, Theropithecus gelada,Papio hamadryas and Papio anubis

Hemoglobins of three baboons, Theropithecus gelada, Papio hamadryas- and Papio anubis, were purified and their oxygen equilibrium characteristics were studied. (a) Oxygen affinity, as expressed by P₅₀, oxygen partial pressure for 50% oxygen binding, was in the order of gelada hemoglobin > anubis hemoglobin > hamadryas hemoglobin although the differences were small. (b) The presence of 2,3-diphosphoglycerate reduced their oxygen affinity in a similar manner. The effect on baboon hemoglobins was greater than that on human and Japanese monkey hemoglobins. (c) The intensity of the Bohr effect, as expressed by $\text{?Δlog}\text{P}{}_{50}\text{ΔpH}$, at pH 7·4 agreed well with each other and the value was 0·62 in the presence of 2 mm diphosphoglycerate and 0·52 in its absence. These results indicate that phenotypic adaptation (acclimatory) may play an important role in the adaptation of gelada baboon to high altitudes.     

Photosynthetic electron transport,ATP synthesis and nitrogenase activity in isolated heterocysts of Anabaena cylindrica

Isolated heterocysts of the N₂-fixing blue-green alga Anabaena cylindrica contain the Photosystem I components P-700, bound and soluble ferredoxins and ferredoxin-NADP reductase. They also show Photosystem I activity being able to photoreduce both methylviologen and NADP when ascorbate+dichlorophenol-indophenol acts as reductant. They photophosphorylate (64 μmol ATP produced/mg chlorophyll $\text{a}\text{h}$) and carry out oxidative phosphorylation (8.7 μmol ATP produced/mg chlorophyll $\text{a}\text{h}$). Ninety per cent of the total cell-free extract nitrogenase activity is located in the heterocyst fraction of aerobic cultures.     

A β-citryl-L-glutamate-hydrolysing enzyme in rat testes

An enzyme responsible for the deacylation of β-citryl-L-glutamate to citrate and glutamate has been characterized in rat testis. The enzyme required manganese ion for full activity and was strongly inhibited by nucleotides such as ATP or GTP. The activity was localized in the particulate fractions. The enzyme favored $\text{N-}\text{formyl-}\text{L}\text{-glutamate}\text{> β-}\text{citryl-}\text{L}\text{-glutamate}\text{> β-}\text{citryl-}\text{L}\text{-glutamine}$ in a decreasing order. The amidohydrolyase activity was highest in the testis and lung, a moderate activity was detected in heart, kidney and intestine, and low in brain, thymus, stomach, skeletal muscle, spleen and liver. These findings suggest that the amidohydrolase is different from any of amidohydrolases reported so far, amidohydrolase I (EC 3.5.1.14), II (EC 3.5.1.15), III, N-acetyl-lysine deacylase (EC 3.5.1.17) and N-acetyl-β-alanine deacetylase (EC 3.5.1.21), and various peptidases.     

Progesterone-induced inactivation of nuclear estrogen receptor in the hamster uterus is mediated by acid phosphatase

Inactivation of hamster uterine estrogen receptor was assayed in nuclear KCl extracts (30 min, 37°C, pH 7.5) after progesterone treatment $\text{in}\text{vivo}$ for 2h. At very low concentrations ($\text{>}$0.05 mM), molybdate and vanadate blocked the progesterone-induced increase in receptor inactivation. In contrast, only high concentrations ($\text{>}$10 mM) of the inhibitors blocked receptor inactivation in extracts from untreated hamsters. Gel electrophoresis and inhibition curves for phosphatases in nuclear extract demonstrated that acid, rather than alkaline, phosphatase activity is most likely responsible for these effects. These data suggest that progesterone antagonizes estrogen action in the hamster uterus by promoting estrogen receptor dephosphorylation leading to inactivation.     

Studies on purine transport and on purine content in vacuoles isolated from Saccharomyces cerevisiae

The transport of purine derivatives into vacuoles isolated from Saccharomyces cerevisiae was studied. Vacuoles which conserved their ability to take up purine compounds were prepared by a modification of the method of polybase-induced lysis of spheroplasts.Guanosine > inosine = hypoxanthine > adenosine were taken up with decreasing initial velocities, respectively; adenine was not transported.Guanosine and adenosine transporting systems were saturable, with apparent K_m values 0.63 mM and 0.15 mM respectively, while uptake rates of inosine and of hypoxanthine were linear functions of their concentrations.Adenosine transport in vacuoles appeared strongly dependent on the growth phase of the cell culture.The system transporting adenosine was further characterized by its pH dependency optimum of 7.1 and its sensitivity to inhibition by $\text{S-}\text{adenosyl-}\text{l}\text{-methionine}$.In the absence of adenosine in the external medium, [¹⁴C]adenosine did not flow out from preloaded vacuoles. However, in the presence of external adenosine, a very rapid efflux of radioactivity was observed, indicating an exchange mechanism for the observed adenosine transport in the vacuoles.In isolated vacuoles the only purine derivative accumulated was found to be $\text{S-}\text{adenosyl-}\text{l}\text{-homocysteine}$.     

The effects of environmental factors on growth and the chemical and biochemical composition of marine diatoms. I. Light and temperature effects

Temperature and light interact to modify the chemical and biochemical composition of a nitrogen-limited marine diatom, Thalassiosira allenii Takano, grown at a constant dilution rate in continuous culture and under a light:dark cycle.The percent of the total ¹⁴C incorporated into protein, polysaccharide and lipid, the N/C ratio and the C/cell varied with temperature in a markedly non-linear manner. The N/cell was negatively correlated to temperature. The Chl $\text{a}\text{C}$ ratio was positively correlated with temperature under saturating light and non-saturating light for temperatures > 25 °C, but was constant under non-saturating light conditions for temperatures < 25 °C.Productivity index (PI) was negatively correlated to temperature under saturating light conditions, but did not vary under low light. In each case, the variation in PI with temperature was governed by the variation in Chl $\text{a}\text{C}$.The dark carbon loss rate was exponentially related to temperature and independent of light. Variation in the percent of the total ¹⁴C incorporated into protein and polysaccharide, the $\text{N}\text{C}$ ratio and C/cell was primarily due to the effects of N-limitation < 20 °C and primarily due to the effects of temperature > 20 °C. Variation in N/cell was primarily due to the effects of temperature over the entire range of temperature studied. Variation in Chl $\text{a}\text{C}$ was caused by the interaction of temperature and light effects.In most cases, temperature and nutrient effects interacted to govern how a particular parameter varied with temperature while light affected the range of values over which the parameter varied.The percent of the total ¹⁴C incorporated into protein exhibited a significant linear relationship with $\text{N}\text{C}$.The dark carbon loss rate, $\text{N}\text{C}$ ratio and Chl $\text{a}\text{C}$ ratio data were used to test the applicability of a model for the physiological adaptation of unicellular algae. The model, with parameters derived from a non-linear least-squares fit of the dark carbon loss rate data, adequately described the $\text{N}\text{C}$ ratio between 15 and 25 °C at 290 and 137 μE · m^?2 · s^?1, but failed to describe the data at 28 °C and at 48 μE · m^?2 · s^?1. The Chl $\text{a}\text{C}$ ratio was adequately described by the model under all light and temperature conditions.     

Localization of photosynthetic electron transport components in mesophyll and bundle sheath chloroplasts of Zea mays

The organization of the electron transport components in mesophyll and bundle sheath chloroplasts of Zea mays was investigated. Grana-containing mesophyll chloroplasts (chlorophyll a to chlorophyll b ratio of about 3.0) possessed the full complement of the various electron transport components, comparable to chloroplasts from C₃ plants. Agranal bundle sheath chloroplasts ($\text{Chl}\text{a}\text{Chl}\text{b}\text{> 5.0}$) contained the full complement of photosystem (PS) I and of cytochrome (cyt) f but lacked a major portion of PS II and its associated Chl $\text{a}\text{b}$ light-harvesting complex (LHC), and most of the cyt b₅₅₉. The kinetic analysis of system I photoactivity revealed that the functional photosynthetic unit size of PS I was unchanged and identical in mesophyll and bundle sheath chloroplasts. The results suggest that PS I is contained in stroma-exposed thylakoids and that it does not receive excitation energy from the Chl $\text{a}\text{b}$ LHC present in the grana. A stoichiometric parity between PS I and cyt f in mesophyll and bundle sheath chloroplasts indicates that biosynthetic and functional properties of cyt f and P₇₀₀ are closely coordinated. Thus, it is likely that both cyt f and P₇₀₀ are located in the membrane of the intergrana thylakoids only. The kinetic analysis of PS II photoactivity revealed the absence of PS II_αfrom the bundle sheath chloroplasts and helped identify the small complement of system II in bundle sheath chloroplasts as PS II_β. The distribution of the main electron transport components in grana and stroma thylakoids is presented in a model of the higher plant chloroplast membrane system.     

Trichinella spiralis: Characterization and strain distribution of rapid expulsion in inbred mice

Appropriately immunized mice display a response that is biologically equivalent to rat rapid expulsion. Only two inbred strains ($\text{NFR}\text{N}\text{and}\text{NFS}\text{N}$ derived from NIH Swiss mice) have been shown to respond in this manner. Mice of the $\text{Balb}\text{c}$, CBA, $\text{A}\text{He}$, C₃H, SJL, or C₅₇Bl strains are “nonresponders” which require approximately twice as much intestinal exposure (in days) to Trichinella spiralis to elicit a response half as effective. Genetically, the responder is dominant, autosomal, and does not appear to be linked to the MHC. The characteristics of mouse and rat rapid expulsion of T. spiralis are not identical but share these features: initial rejection within 24 hr of challenge; a rejection efficiency >90%, from 1 to 5 weeks after the primary; induction of response does not require exposure to the complete infection; rapid expulsion is immunologically specific for preadults; adult worms are resistant. While a genetic basis for responsiveness exists in mice there is, as yet, no evidence for genetic control in rats. In both mice and rats, rapid expulsion is distinguished from the intestinal hyperreactivity associated with rejection of the primary infection by the kinetics and amplitude of the rejection of transplanted adult worms.     

Dissociation between Ca2+-ATPase and alkaline phosphatase activities in plasma membranes of rat duodenum

The presence of Ca²⁺-ATPase activities with high-affinity sites for Ca²⁺ in brush border as well as basolateral plasma membranes of rat duodenal epithelium has been reported previously (Ghijsen, W.E.J.M. and van Os, C.H. (1979) Nature 279, 802–803). Since both plasma membranes contain alkaline phosphatase (EC 3.1.3.1), which also can be stimulated by Ca²⁺, the substrate specificity of Ca²⁺-induced ATP-hydrolysis has been studied to determine whether or not alkaline phosphatase and Ca²⁺-ATPase are two distinct enzymes. In basolateral fragments, the rate of Ca²⁺-dependent ATP-hydrolysis was greater than that of ADP, AMP and $\text{p-}\text{nitrophenylphosphate}$ at Ca²⁺ concentrations below 25 μM. At 0.2 mM Ca²⁺ the rates of ATP, ADP, AMP and $\text{p-}\text{nitrophenylphosphate}$ hydrolysis were not significantly different. In brush border fragments the rates of ATP, ADP and AMP hydrolysis were identical at low Ca²⁺, but at 0.2 mM Ca²⁺, Ca²⁺-induced hydrolysis of ADP and AMP was greater than either ATP or $\text{p-}\text{nitrophenylphosphate}$. Alkaline phosphatase in brush border and basolateral membranes was inhibited by 75% after addition of 2.5 mM theophylline. Ca²⁺-stimulated ATP hydrolysis at 1 μM Ca²⁺ was not sensitive to theophylline in basolateral fragments while the same activity in brush border fragments was totally inhibited. At 0.2 mM Ca²⁺, Ca²⁺-induced ATP hydrolysis in both basolateral and brush border membranes was sensitive to theophylline. Oligomycin and azide had no effect on Ca²⁺-stimulated ATP hydrolysis, either at low or at high Ca²⁺ concentrations. Chlorpromazine fully inhibited Ca²⁺-stimulated ATP hydrolysis in basolateral fragments at 5 μM Ca²⁺, while it had no effect in brush border fragments. From these results we conclude that, (i) Ca²⁺-ATPase and alkaline phosphatase are two distinct enzymes, (ii) high-affinity Ca²⁺-ATPase is exclusively located in basolateral plasma membranes, (iii) alkaline phosphatase activity, present on both sides of duodenal epithelium, is stimulated slightly by low Ca²⁺ concentrations, but this Ca²⁺-induced activity is inhibited by theophylline and shows no specificity with respect to ATP, ADP or AMP.     

Isolation and characterization of Photosystem I and II membrane particles from the blue-green alga, Synechococcus cedrorum

Fractions enriched in either Photosystem I or Photosystem II activity have been isolated from the blue-green alga, Synechococcus cedrorum after digitonin treatment. Sedimentation of this homogenate on a 10–30% sucrose gradient yielded three green bands: the upper band was enriched in Photosystem II, the lowest band was enriched in Photosystem I, while the middle band contained both activities. Large quantities of both particles were isolated by zonal centrifugation, and the material was then further purified by chromatography on DEAE-cellulose.The resulting Photosystem II particles carried out light-induced electron transport from semicarbizide to ferricyanide of over 2000 μmol/mg Chlorophyll per h (which was sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea), and was nearly devoid of Photosystem I activity. This particle contains β-carotene, very little phycocyanin, has a chlorophyll absorption maximum at 675 nm, and a liquid N₂ fluorescence maximum at 685 nm. The purest Photosystem II particles have a chlorophyll to cytochrome $\text{b-559}$ ratio of 50 : 1. The Photosystem I particle is highly enriched in $\text{P-700}$, with a chlorophyll to $\text{P-700}$ ratio of 40 : 1. The physical structure of the two Photosystem particles has also been studied by gel electrophoresis and electron microscopy. These results indicate that the size and protein composition of the two particles are distinctly different.     

Pressure effects on lipid-protein interactions in (Na+ + K+)-ATPase

The (Na⁺ + K⁺)-stimulated ATPase activity decreases with increasing pressure and a plot of the logarithm of the activity versus pressure shows a change in slope at a defined breakpoint pressure (P_b). The value of P_b increases linearly with increasing temperature. A $\text{d}\text{T}\text{d}\text{P}$ value of 27.7 ± 0.4 (S.D.) K/1000 atm is obtained. This is in very good agreement with the pressure shift for the melting transitions in phospholipids and aliphatic chains. This strongly indicates that an aliphatic chain melting process is involved in the breakpoint in the Arrhenius plot and pressure dependence of (Na⁺ + K⁺)-ATPase. The p-nitrophenyl phosphatase activity of this enzyme also decreases with pressure. In this case the plot of the logarithm of the activity versus pressure is linear without a break-point. The temperature dependence for (Na⁺ + K⁺)-ATPase was also studied in the presence of fluidizing drugs: desipramine and benzylalcohol. The presence of these drugs had no effect on the inflection point in the Arrhenius plot.     

The adenylate energy charge in marine phytoplantkon: The effect of temperature on the physiological state of Skeletonema costatum (Grev.) Cleve

The adenylate energy charge $\text{([ATP] +}\text{1}\text{2}\text{[ADP])}\text{[0ATP+ADP+AMP]}$ was measured in axenic batch cultures of Skeletonema costatum (Grev.) Cleve at 2°, 10°, 15°, 20°, 24° and 30°C. The results suggest that this eurythermal diatom is physiologically capable of adapting to the 28 °C range of temperature with little apparent difference in the potential energy available to the cell. In N-limited continuous cultures at 15 °C, the energy charge values were lower than those observed in batch culture by 0.2, implying nutrient stress may result in decreased intracellular chemical energy. The utilization of the adenylate energy charge as an indicator of physiological state is suggested.     

Biphasic effect on platelet aggregation by phospholipase a purified from Vipera russellii snake venom

A basic phospholipase A was isolated from Vipera russellii snake venom. It induced a biphasic effect on washed rabbit platelets suspended in Tyrode's solution. The first phase was a reversible aggregation which was dependent on stirring and extracellular calcium. The second phase was an inhibitory effect on platelet aggregation, occurring 5 min after the addition of the venom phospholipase A without stirring or after a recovery from the reversible aggregation. The aggregating phase could be inhibited by indomethacin, tetracaine, papaverine, creatine phosphate/creatine phosphokinase, mepacrine, verapamil, sodium nitroprusside, prostaglandin E₁ or bovine serum albumin. The venom phospholipase A released free fatty acids from synthetic phosphatidylcholine and intact platelets. $\text{p-}\text{Bromophenacyl}$ bromide-modified venom phospholipase A lost its phospholipase A enzymatic and platelet-aggregating activities, but protected platelets from the aggregation induced by the native enzyme. The second phase of the venom phospholipase A action showed a different degree of inhibition on platelet aggregation induced by some activators in following order: $\text{arachidonic acid}\text{>}\text{collagen}\text{>}\text{thrombin}\text{>}\text{ionophore A}\text{23187}$. The longer the incubation time or the higher the concentration of the venom phospholipase A, the more pronounced was the inhibitory effect. The venom phospholipase A did not affect the thrombin-induced release reaction which was caused by intracellular Ca²⁺ mobilization in the presence of EDTA, but inhibited collagen-induced release reaction which was caused by Ca²⁺ influx from extracellular medium. The inhibitory effect of the venom phospholipase A and also lysophosphatidylcholine or arachidonic acid could be antagonized or reversed by bovine serum albumin. It was concluded that the first stimulatory phase of the venom phospholipase A action might be due to arachidonate liberation from platelet membrane. The second phase of inhibition of platelet aggregation and the release of ATP might be due to the inhibitory action of the split products produced by this venom phospholipase A.     

Alkaline phosphatase and maltase activity in the embryonic chick intestine in culture. Influence of thyroxine and hydrocortisone.

In strips of duodenum from 14-day chick embryos explanted into defined medium, alkaline phosphatase (ALP) activity accumulated in the tissue at a faster rate than in vivo for about 48 hr, but failed to increase thereafter. The addition of thyroxine (T4) to the medium at 10^?8M or less both enhanced the early accumulation and elicited a very large increase in ALP activity comparable to that normally occurring during the last 2 days in ovo. Activity with phenylphosphate (PhP) was more strongly affected than that with β-glycerophosphate (βGP), so that the high $\text{PhP}\text{β}\text{GP}$ ratio attained in vivo at 18 days was reached after 24 hr in T4-supplemented medium. Hydrocortisone (HC) evoked APL activity only slightly above that in unsupplemented medium and only during the first 48 hr in culture, but it precociously elevated $\text{PhP}\text{β}\text{GP}$ ratio to the normal maximum. In the presence of T4 or HC, maltase activity rose in explanted strips at the same rate as in the intact duodenum, but it lagged in unsupplemented medium. Assay of the medium revealed, however, that under all conditions of culture a large amount of both maltase and ALP activity had been released from the tissue. This effect was especially pronounced in the presence of T4, so that explants and medium together accumulated ALP and maltase equivalent to the high peaks of activity found in the intact duodenum at hatching. With 10^?8M T4, ALP activity began to rise above that of control explants after 8 hr, with accumulation in the medium beginning about 4 hr later. Combining 2 × 10^?6M HC with a range of T4 concentrations produced greater than additive effects, particularly with ALP, but did not lead to enhanced retention of either enzyme in the tissue strips. Prolactin, pentagastrin, and insulin were without effect alone, but the latter inhibited the effects of both T4 and HC.     

Oxidative phosphorylation by membrane vesicles from Bacillus alcalophilus

ADP and P_i-loaded membrane vesicles from l-malate-grown Bacillus alcalophilus synthesized ATP upon energization with $\text{ascorbate}\text{N,N,N′,N′-}\text{tetramethyl}\text{-p-}\text{phenylenediamine}$. ATP synthesis occurred over a range of external pH from 6.0 to 11.0, under conditions in which the total protonmotive force was as low as ?30 mV. The phosphate potentials (ΔG_p) were calculated to be 11 and 12 kcal/mol at pH 10.5 and 9.0, respectively, whereas the values in vesicles at these two pH values were quite different (?40 ± 20 mV at pH 10.5 and ?125 ± 20 mV at pH 9.0). ATP synthesis was inhibited by KCN, gramicidin, and by N,N′-dicyclohexylcarbodiimide. Inward translocation of protons, concomitant with ATP synthesis, was demonstrated using direct pH monitoring and fluorescence methods. No dependence upon the presence of Na⁺ or K⁺ was found. Thus, ATP synthesis in B. alcalophilus appears to involve a proton-translocating ATPase which functions at low .     

Early stimulation of alkaline phosphatase activity in response to 1 alpha, 25-dihydroxycholecalciferol.

Alkaline phosphatase activity (APA) stimulation in response to 1,25-dihydroxycholecalciferol (1,25 (OH)₂D₃) has been studied in vitamin-D-deficient rat intestinal brush borders prepared from $\text{ex}$-$\text{vivo}$-perfused duodeno-jejunal segments. Basal APA in intestines perfused with ethanol remained constant throughout the experiments. APA was significantly increased when intestines were perfused with 1,25 (OH)₂D₃ (3 nM) for 30, 45 or 60 min. A dose-effect response was observed when 1,25 (OH)₂D₃ increased in the perfusion medium. The maximal alkaline phosphatase activity after a 45-min perfusion (2404 ± 379 m^TU/mg prot.) was observed when 1,25 (OH)₂D₃ concentration was 6 nM. Cholecalciferol had no effect in this system.     

The purification and characterization of Dictyostelium discoideum plasma membranes

A new procedure for the purification of plasma membranes of Dictyostelium discoideum is described. Cells are broken by vigorously stirring in the presence of glass beads, and plasma membranes are isolated by equilibrium sucrose density centrifugation. The purified membranes are considerably enriched in alkaline phosphatase and 5′-nucleotidase and contain very low levels of succinate dehydrogenase and NADPH-cytochrome $\text{c}$ reductase. The purified membranes contain relatively high levels of phospholipid, sterol and carbohydrate. They appear as a relatively homogeneous population of membrane vesicles in the electron microscope. This new method of purification is compared to previously published procedures which have been found to be unsuitable for our purposes.     

Plasmodium berghei: Thyroid hyperplasia and thyroid hyperactivity in mice

Statistically significant (P < 0.05) thyroid hyperactivity (¹³¹I% uptakes) occurs on certain days in Plasmodium berghei infected C3H mice. Male mice thyroid glands are made more hyperactive by the malaria than the female glands. Hyperactive thyroid glands may be at least one cause of hypocholesterolemia in plasmodium-infected rodents. Thyroid hyperplasia was found only in experimental mice ($\text{6}\text{20}$ males; $\text{8}\text{20}$ females). A hyperactive thyroid gland appears to be an unreported aspect of experimental acute P. berghei infections in mice. The hyperthyroidism may be due to possible toxic substances acting either directly on the thyroid gland, or indirectly on the hypothalamus affecting TSH production.