Circadian and seasonal variation of the body temperature of sheep in a tropical environment

Nychthemeral and annual rhythms of the rectal temperature were determined for Corriedale sheep in a tropical climate. The minimum rectal temperature averaged 39.55° C at 0500 hours in summer, and 38.87° C at 0600 hours in winter. The maximum was 40.03° C in summer (1700 hours) and 39.33° C in winter (1830 hours). Annual cycle of the rectal temperature showed a minimum in July and maximum in December.     

Functional and genetic analysis of annexin VI

This study is concerned with the determination of the function of the 68kDa calcium-binding protein, annexin VI. Studies on the structure and regulation of the gene include a detailed analysis of annexin VI expressed heterologously in human A431 carcinoma cells. We have recently discovered that annexin VI is subject to a novel growth dependent post-translational modification. Interestingly, the protein exerts a negative effect on A431 cells. This effect was manifested as a partial reversal of the transformed phenotype. We are currently exploring the hypothesis that the post-translational modification of annexin VI is required for sub-cellular targeting, and that correct localisation within the cell is essential for function.     

PEST sequences in calmodulin-binding proteins

Many short-lived proteins which are devoid of proteolytic activity contain PEST sequences which are segments along the polypeptide chain that are rich in proline (P), glutamate (E), serine (S) and threonine (T). These designated PEST sequences are believed to be putative intramolecular signals for rapid proteolytic degradation. Calmodulin is a ubiquitous, 17kDa, acidic Ca²⁺-binding protein which plays an important role in the regulation of many physiological processes through its interaction with a wide range of calmodulin-binding proteins. Several calmodulin-binding proteins are known to contain PEST sequences and are susceptible to proteolysis by endogenous neutral proteases such as calpain I and calpain II. In this report, we discuss the functions of PEST sequences in calmodulin-binding proteins and assess the correlation between calmodulin-binding proteins and PEST sequences.     

Evidence for two possible glnB-type genes in Herbaspirillum seropedicae.

Two glnB-like genes have been isolated from Herbaspirillum seropedicae by complementation of the Klebsiella pneumoniae glnB502 mutant for growth on nitrate. One of these glnB-like genes has been sequenced and shows strong identity with GlnB proteins derived from other organisms. A Tn5-20 mutation of this glnB was Nif negative.     

Nociceptive atrophy of the rat soleus muscle induced by bone fracture: a morphometric study

Zachaová, Gisela, HelenaKnotková-Urbancová, Pavel Hník, andTomá Soukup. Nociceptive atrophy of the rat soleus muscle induced by bone fracture: a morphometric study.J. Appl. Physiol. 82(2): 552-557, 1997.Reflex atrophy of the soleus muscle induced by ipsilateralmetatarsal bone fracture in Sagatal-anesthetized adult male rats wasstudied by using two-dimensional stereological methods 7 days after theoperation. When compared with contralateral solei, the wet weight ofthe experimental soleus muscles was decreased by ~24% and the areaof the entire muscle section by ~29%. In atrophied solei, the numberof type 1 fibers was lower by ~8%, resulting in lower total numberof fibers (by ~6%). This indicates that slow motor units might bemore sensitive to nociceptive stimulation. However, with respect to thefiber area, the reflex atrophy induced by metatarsal bone fracture inthe rat soleus muscle resembles simple atrophy after 7 days, as themean muscle fiber area was decreased by ~26% with no significantdifference between atrophy in type 1 and type 2a fibers (by 27.3 and23.0%, respectively).

     

Comparative Physiology of Dimethyl Sulfide Production by Dimethylsulfoniopropionate Lyase in Pseudomonas doudoroffii and Alcaligenes sp. Strain M3A

Dimethylsulfoniopropionate (DMSP) lyase enzymatically cleaves DMSP, an algal metabolite, to produce acrylate, a proton, and dimethyl sulfide (DMS), the most abundant volatile sulfur compound emitted from oceans. The physiology of DMS production by DMSP lyase was studied in vivo in an Alcaligenes-like organism, strain M3A, a salt marsh bacterial isolate, and in a marine strain, Pseudomonas doudoroffii. Enzymes from both strains were induced at optimum rates by 1 mM DMSP and vigorous aeration. P. doudoroffii was very sensitive to continued aeration and lost activity rapidly; the enzyme was more stable when aeration ceased. In addition to DMSP, acrylate and several of its analogs acted as inducers of DMSP lyase in Alcaligenes sp. strain M3A but not in P. doudoroffii. Turnover of DMSP by P. doudoroffii was enhanced by 3.5% NaCl or seawater, whereas the Alcaligenes sp. strain M3A enzyme was not salt dependent and salt did not greatly affect its activity. The pH profile showed two peaks of DMSP lyase activity (6.5 and 8.8) for Alcaligenes sp. strain M3A and a single peak at pH 8 for P. doudoroffii. Enzyme activity in both organisms was inhibited by methyl-3-mercaptopropionate and homocysteine. Cyanide, azide and p-chloromercuribenzoate inhibited only the P. doudoroffii DMSP lyase. The apparent K(infm) values for DMSP for cell cultures of Alcaligenes sp. strain M3A and P. doudoroffii were ca. 2 mM and <20 (mu)M, respectively. The differences in the physiology of DMSP metabolism in these two bacterial isolates may enable them to exist in diverse ecological niches.     

Intracellular serine proteinase behaves as a heat-stress protein in nongrowing but as a cold-stress protein in growing populations of Bacillus megaterium

A temperature increase from 35° to 40–42°C enhances the rise of cytoplasmic serine proteinase (ISP1) activity in Bacillus megaterium incubated in a sporulation medium. A temperature shift from 27°C in the growth medium to 35°C in the sporulation medium has the same effect. Elevated temperature stimulates the increase of ISP1 level when applied immediately after the transfer of cells from the growth to the sporulation medium (at T₀) or at T₃, when sporulation becomes irreversible. The cytoplasmic PMSF-resistant activity or the proteolytic activity associated with the membrane fraction is stimulated only slightly or not at all. A temperature increase to 45–47°C suppresses the rise of proteolytic activities in all cell fractions. In addition to the elevation of the ISP1 activity by an upward temperature shift, the rise of this enzyme in nongrowing cells is also stimulated by osmotic stress. In growing populations, in contrast to the rise of the ISP1 activity caused by elevated temperature in nongrowing cells, this proteinase is induced by low temperatures (24–27°C). The ISP1 activity roughly correlates with the enzyme protein concentration determined by immunoblotting.     

Neurochemical effects ofl-pyroglutamic acid

The effect ofl-pyroglutamic acid, a metabolite that accumulates in pyroglutamic aciduria, on different neurochemical parameters was investigated in adult male Wistar rats. Glutamate binding, adenylate cyclase activity and G protein coupling to adenylate cyclase were assayed in the presence of the acid.l-pyroglutamic acid decreased Na⁺-dependent and Na⁺-independent glutamate binding Basal and GMP-PNP stimulated adenylate cyclase activity were not affected by the acid. Furthermore, rats received unilateral intrastriatal injections of 10–300 nmol of bufferedl-pyroglutamic acid. Vehicle (0.25 M Tris-Cl, pH 7.35–7.4) was injected into the contralateral striatum. Neurotoxic damage was assessed seven days after the injection by histological examination and by weighing both cerebral hemispheres. No difference in histology or weight could be identified between hemispheres. These results suggest that, although capable of interfering with glutamate binding, pyroglutamate did not cause a major lesion in the present model of neurotoxicity.