Conformational changes of recombinant human granulocyte-colony stimulating factor induced bypH and guanidine hydrochloride

Fluorescence and circular dichroism were used to follow thepH-dependent conformational changes of granulocyte colony stimulating factor (G-CSF). Tryptophan fluorescence of the spectra monitored at 344 nm, or after deconvolution of the emission spectra, at 345 nm, showed a decrease in intensity on going frompH 7 to 4, with a midtransitionpH of 5.8. On the other hand, tyrosine fluorescence measured either by the ratio of intensity at 308 nm to that at 344 nm, or by the fluorescence intensity at 303 nm after deconvolution of the spectra, increased in intensity as thepH was changed from 6 to 2.5, with a midtransitionpH of 4.5. Near UV circular dichroic spectra also showed changes betweenpH 7.5 and 4.5, which correlated with the transition monitored by the tryptophan fluorescence. The guanidine hydrochloride-induced conformational changes of G-CSF at fivepH values from 2.5 to 7.5 were also studied. Circular dichroic and fluorescence spectra revealed minor conformational changes by the addition of 1 or 2 M guanidine HCl at allpH values examined, while the major conformational transition occurred between 2 and 4 M guanidine hydrochloride. The secondary structure of the protein was most stable betweenpH 3.3 and 4.5. The guanidine HCl-induced denaturation of G-CSF involved more than a two-state transition, with detectable intermediate(s) present, and the structure of the intermediate(s) appeared to depend on thepH used. These results are consistent with thepH dependence of the structure described above, and demonstrate the complex conformational properties of G-CSF.     

Brain Cytochrome Oxidase in Alzheimer''s Disease

A recent demonstration of markedly reduced (-50%) activity of cytochrome oxidase (CO; complex 4), the terminal enzyme of the mitochondrial enzyme transport chain, in platelets of patients with Alzheimer's disease (AD) suggested the possibility of a systemic and etiologically fundamental CO defect in AD. To determine whether a CO deficiency occurs in AD brain, we measured the activity of CO in homogenates of autopsied brain regions of 19 patients with AD and 30 controls matched with respect to age, postmortem time, sex, and, as indices of agonal status, brain pH and lactic acid concentration. Mean CO activity in AD brain was reduced in frontal (-26%: p less than 0.01), temporal (-17%; p less than 0.05), and parietal (-16%; not significant, p = 0.055) cortices. In occipital cortex and putamen, mean CO levels were normal, whereas in hippocampus, CO activity, on average, was nonsignificantly elevated (20%). The reduction of CO activity, which is tightly coupled to neuronal metabolic activity, could be explained by hypofunction of neurons, neuronal or mitochondrial loss, or possibly by a more primary, but region-specific, defect in the enzyme itself. The absence of a CO activity reduction in all of the examined brain areas does not support the notion of a generalized brain CO abnormality. Although the functional significance of a 16-26% cerebral cortical CO deficit in human brain is not known, a deficiency of this key energy-metabolizing enzyme could reduce energy stores and thereby contribute to the brain dysfunction and neurodegenerative processes in AD.     

New records of within-group infanticide and cannibalism in wild chimpanzees

Two cases of within-group infanticide and cannibalism were observed among the M Group chimpanzees of the Mahale Mountains, Tanzania. In both cases, victimized infants were male, 5 – 6 months of age, and in good health when killed. Four to five years have passed since the mothers of the victims immigrated into M Group as nulliparous immigrants. In one case the 2nd-ranking male was observed to detach the infant from the mother's belly. Both infants were finally killed by the alpha male after several adult males scrambled for the bodies. There was no evidence that the mothers had mated with males other than those of M Group. Nor was there evidence that the mothers had restrictive mating relationships with some of the M Group adult males. What little evidence is available shows that the mothers had mated mostly with adolescent and other immature males during their conception cycles. However, at least in one case, the mother began to mate more with adult males rather than with immature males after the infanticide. It is proposed that the function of within-group male infanticide can be explained by the male-male competition hypothesis developed for hanuman langurs and other nonhuman primates.     

''Trouble-shooting'' microwave accelerated procedures in histology and histochemistry: understanding and dealing with artefacts, errors and hazards

Summary Heating by microwave irradiation (microwaving) is a controllable way to accelerate most processes of diffusion and many chemical reactions occurring in histoprocessing and histochemistry. Consequently, microwaving can be particularly time-saving. However, apart from desirable accelerations, unwanted diffusions and reactions may also occur. These can generate artefacts such as extraction of tissue components, chemical alterations of cellular content, and decomposition of thermally labile staining reagents. Artefacts may arise at all stages of histoprocessing, from fixation, through embedding, to staining. Whereas all artefacts result from heating, some specifically involve microwave ovens; e.g. irregular heating due to inhomogeneities in the microwave field, and ageing of the magnetron.Microwaving can involve certain hazards. Most of them also arise in conventional ovens, but a few are unique to microwave ovens; for example, aqueous contents heating faster than glass containers, and sparking due to labels written in pencil. The trouble-shooting of microwave procedures requires an understanding of the nature of the heating process and of the procedure in question. In order to achieve this, the development and application of trouble-shooting charts for commonly used procedures is both recommended and illustrated.     

The genetic defect in multiple endocrine neoplasia type 2A maps next to the centromere of chromosome 10

Multiple endocrine neoplasia type 2A (MEN2A) is a rare cancer syndrome that is inherited in an apparently autosomal dominant fashion. Previous linkage studies had assigned the MEN2A locus to chromosome 10 in the pericentromeric region. We recently have described several new easily scorable RFLPs for the chromosome 10-specific alpha satellite DNA (the D10Z1) locus that is known, on the basis of previous in situ hybridization experiments, to lie at the centromere. We report here tight linkage between MEN2A and D10Z1, as demonstrated by a maximum lod score of 12.02 at the recombination frequency of zero (1-lod-unit support interval 0-4 cM), indicating that the genetic defect in MEN2A lies in the immediate vicinity of the centromere. By means of a set of ordered polymorphic DNA markers from the pericentromeric region, multipoint as well as pairwise linkage analyses place the MEN2A locus at the middle of a small region (approximately 11 cM) bracketing the centromere with FNRB (at 10p11.2) and RBP3 (at 10q11.2) on either side, providing further support for the centromeric location of the MEN2A locus. Marked sex difference in recombination frequencies exists in this pericentromeric region: significantly (P less than .01) more female than male crossovers were observed across all of the adjacent intervals D10S24-FNRB, FNRB-D10Z1, and D10Z1-RBP3. However, a sex difference was not seen in the 7-cM interval from RBP3 to D10S5, suggesting that large variation in the sex difference in recombination can occur over small chromosomal regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preferential Osmolyte Accumulation: a Mechanism of Osmotic Stress Adaptation in Diazotrophic Bacteria

A common cellular mechanism of osmotic-stress adaptation is the intracellular accumulation of organic solutes (osmolytes). We investigated the mechanism of osmotic adaptation in the diazotrophic bacteria Azotobacter chroococcum, Azospirillum brasilense, and Klebsiella pneumoniae, which are adversely affected by high osmotic strength (i.e., soil salinity and/or drought). We used natural-abundance ¹³C nuclear magnetic resonance spectroscopy to identify all the osmolytes accumulating in these strains during osmotic stress generated by 0.5 M NaCl. Evidence is presented for the accumulation of trehalose and glutamate in Azotobacter chroococcum ZSM4, proline and glutamate in Azospirillum brasilense SHS6, and trehalose and proline in K. pneumoniae. Glycine betaine was accumulated in all strains grown in culture media containing yeast extract as the sole nitrogen source. Alternative nitrogen sources (e.g., NH₄Cl or casamino acids) in the culture medium did not result in measurable glycine betaine accumulation. We suggest that the mechanism of osmotic adaptation in these organisms entails the accumulation of osmolytes in hyperosmotically stressed cells resulting from either enhanced uptake from the medium (of glycine betaine, proline, and glutamate) or increased net biosynthesis (of trehalose, proline, and glutamate) or both. The preferred osmolyte in Azotobacter chroococcum ZSM4 shifted from glutamate to trehalose as a consequence of a prolonged osmotic stress. Also, the dominant osmolyte in Azospirillum brasilense SHS6 shifted from glutamate to proline accumulation as the osmotic strength of the medium increased.     

Burrowing behaviour in the crayfish, Cambarus diogenes diogenes girard

The crayfish, Cambarus diogenes diogenesGirard (1852), spends most of its life cycle in individually constructed underground burrows. The architectural behavioral patterns and sequences with which adult C. d. diogenes excavate an underground chamber were evaluated. Two motor patterns (Pushing and Carrying) and three burrow stages (shallow depression, angular pit, and burrow with two openings) were identified. During the development of burrowing behaviour in juveniles, a third motor pattern (Fanning) occurred. While the three motor patterns are functional soon after hatching, crayfish may learn to orient the Carrying motor pattern for the most efficient excavation of a stage-3 burrow with two openings. The ground-water level determined the final structure of a burrow.     

Development of a Defined Medium for Growth of Cercospora rosicola Passerini

A simple synthetic liquid medium containing a single amino acid, glucose, salts, trace metals, and thiamine was developed for cultivation of Cercospora rosicola Passerini. Thiamine was shown to be important to growth. Culture of C. rosicola Passerini in a chemically defined medium makes possible studies of (+)-abscisic acid biosynthesis and regulation.