Coefficients of digestibility and nutritional values of geophytes and tubers eaten by southern African mole-rats (Rodentia: Bathyergidae)

Subterranean rodents have high energy requirements when they are excavating their burrows. This study investigates the energy available to, and the efficiency with which it can be extracted by, four species of bathyergid mole-rats fed natural diets ranging from the underground storage organs of geophytes to grass roots and leaves.
The digestibility coefficients of geophytes ranged from 53% for the fibrous tuber of the gemsbok cucumber to 95–7% for corms and bulbs. One species, Bathyergus suillus whose diet consists of over 80% grass, had a digestibility coefficient of 87% on an all grass diet.
All species had similar coefficients of digestibility of > 90% when fed on a uniform diet of sweet potato.
Bulbs and corms had a low fibre content (3–3–4%), high calorific value (15–16kJ/g) and high digestibility coefficients (95–7–96%) and on this diet the mole-rats maintained their body mass. Food of lower digestibility tended to have a high fibre content (8–2–45%) and, with the exception of B. suillus , although the mole-rats consumed a greater quantity of food, they lost mass. The sweet potato had a low fibre content (4–1 %) but was energetically very similar to bulbs and corms (15–5 kJ/g).
Geophytes which have low fibre contents are generally small (1–20 g), whereas geophytes with high fibre contents are much larger (30–2000 g) and often occur in more arid zones.     

Production of Verrucarol

Verrucarol was obtained from a simple procedure that involved the hydrolysis of a crude extract of a culture of Myrothecium verrucaria ATCC 24571.     

Differentiation of lactic streptococcal phages into phage species by DNA-DNA homology.

Twenty-five lactic streptococcal bacteriophages were differentiated by DNA homology into four species. Complete correlation was found between DNA homology groups and morphological characteristics of the phages except that two phage types, which differed in only the presence or absence of a collar, were one species by DNA homology. These findings were supported by serological data and differences in DNA molecular weights of the proposed species. The complete lack of homology between these phage species indicates that they are unlikely to have a recent common phage ancestor and that one morphological type of phage has not been derived by mutation from a phage of another morphological type.     

Genetic diversity ofRhizobium strains which nodulateLeucaena leucocephala

DNA homologies at 65°C in 0.14 phosphate buffer, pH 6.8, were determined between 24 strains ofRhizobium capable of nodulatingLeucaena leucocephala and fourRhizobium reference strains. Twenty-one strains (88%) were placed in one of four DNA homology groups. The mean relative homology within a group was 65%, while the mean relative homology between groups was 20%. Thermal melting points for reassociated DNA (ΔT_m(e) values) were also measured. The lack of DNA homology between groups indicates that several very different populations of bacteria are capable of nodulating and fixing nitrogen with leucaena.     

Interstitial 3-Methoxytyramine Reflects Striatal Dopamine Release: An In Vivo Microdialysis Study

Previous ex vivo studies have provided indirect evidence that the dopamine (DA) metabolite 3-methoxytyramine (3-MT) may be a useful index of DA release in vivo. In the present study, in vivo microdialysis was utilized to assess directly the relationship between extracellular DA and 3-MT in the striatum of rats following a variety of pharmacological manipulations. Apomorphine, a DA receptor agonist, produced a rapid, transient decrease in both DA and 3-MT. Conversely, the DA receptor antagonist haloperidol produced a concomitant increase in extracellular DA and 3-MT. Increases in DA and 3-MT were also noted following the administration of the DA uptake inhibitor, bupropion. Local application of tetrodotoxin resulted in the complete elimination of measurable amounts of DA and 3-MT in the dialysate, gamma-Butyrolactone also greatly decreased DA and 3-MT. Finally, d-amphetamine produced a large increase in DA and 3-MT in animals that had been treated previously with gamma-butyrolactone. The Pearson correlation coefficients for DA and 3-MT following these manipulations ranged from 0.87 to 0.97. These data indicate that interstitial 3-MT is an accurate index of DA release. However, when compared with previous ex vivo findings, the present results also suggest that changes in tissue concentrations of 3-MT may not reliably reflect DA release following certain pharmacological manipulations.     

Baculovirus phosphoprotein pp31 is associated with virogenic stroma.

The PstI K fragment of Autographa californica nuclear polyhedrosis virus (AcMNPV) encodes a protein with a molecular weight of 31,000. To define the role of this protein (pp31) in virus infection further, it was overexpressed in bacteria and used to produce polyclonal antiserum. Radioimmunoprecipitation analysis indicated that pp31 was synthesized during both the early and late phases of virus infection, consistent with previous analyses indicating that the gene was regulated by tandem early and late promoters. Metabolic labeling of cells with carrier-free phosphate indicated that pp31 was phosphorylated. Biochemical fractionation experiments showed that pp31 was localized in the nucleus and that it was more stably associated with the nucleus at later times of infection. Immunoblot analysis of subnuclear fractions indicated that pp31 was associated predominantly with the chromatin and nuclear matrix fractions. Immunofluorescence experiments confirmed that the pp31 protein was localized in the nucleus. Nuclear staining was relatively uniform early but was more centrally nuclear later in infection. Immunoelectron microscopy indicated that the pp31 protein was a component of virogenic stroma. Southwestern (DNA-protein) blot analysis demonstrated that pp31 is a DNA-binding protein. These findings suggest a possible role for pp31 in the virus life cycle.     

The proportion of calcium-bound pectin in plant cell walls

The amount of pectin held in cell walls by ionic bonds only was determined by extraction with cyclohexanediamine tetraacetic acid (CDTA) at room temperature, to remove calcium ions without degrading the galacturonan chains. Enzymic degradation was avoided by extracting the cell walls with phenol-acetic acid-water during preparation. From cell walls of celery petioles, cress hypocotyls and tomato and cucumber pericarp CDTA extracted 64–100 mg g^-1 pectin, leaving 80–167 mg g^-1 uronic acid in the residue. An additional extraction at high ionic strength was used to make the galacturonan chains more flexible and thus detach any pectins held by steric interactions, but the amount released in this way was small. Most of the residual uronic acid polymers could be extracted by cold alkali and remained soluble on neutralisation, showing that it was not water-insolubility that prevented their extraction with CDTA. Covalent bonding was thought more likely.     

The polysaccharide structure of potato cell walls: Chemical fractionation

Cell walls of potato tubers were fractionated by successive extraction with various reagents. A slightly degraded pectic fraction with 77% galacturonic acid was extracted in hot, oxalate-citrate buffer at pH 4. A further, major pectic fraction with 38% galacturonic acid was extracted in cold 0.1 M Na₂CO₃ with little apparent degradation. These two pectic fractions together made up 52% of the cell wall. Most of the oxalate-citrate fraction could alternatively be extracted with cold acetate-N,N,N-tetracetic acid (CDTA) buffer, a non-degradative extractant which nevertheless removed essentially all the calcium ions. This fraction was therefore probably held only by calcium binding, and the remainder of the pectins by covalent bonds. Electrophoresis showed that both pectic fractions contained a range of molecular types differing in composition, with a high arabinose: galactose ratio as well as much galacturonic acid in the most extractable fractions. From methylation data, the main side-chains were 1,4-linked galactans and 1,5-linked arabinans, with smaller quantities of covalently attached xyloglucan. Extraction with NaOH-borate removed a small hemicellulose fraction and some cellulose. The main hemicelluloses were apparently a galactoxyloglucan, a mannan or glucomannan and an arabinogalactan.Abbreviations GLC gas-liquid chromatography - MS mass spectrometry - V₀ void volume - MW weight-average molecular weight - DMSO dimethylsulphoxide - EDTA ethylenediamine tetraacetic acid - TFA trifluoroacetic acid - CDTA N,N,N-tetraacetic acid