Direct Comparisons of 2D and 3D Dental Microwear Proxies in Extant Herbivorous and Carnivorous Mammals

The analysis of dental microwear is commonly used by paleontologists and anthropologists to clarify the diets of extinct species, including herbivorous and carnivorous mammals. Currently, there are numerous methods employed to quantify dental microwear, varying in the types of microscopes used, magnifications, and the characterization of wear in both two dimensions and three dimensions. Results from dental microwear studies utilizing different methods are not directly comparable and human quantification of wear features (e.g., pits and scratches) introduces interobserver error, with higher error being produced by less experienced individuals. Dental microwear texture analysis (DMTA), which analyzes microwear features in three dimensions, alleviates some of the problems surrounding two-dimensional microwear methods by reducing observer bias. Here, we assess the accuracy and comparability within and between 2D and 3D dental microwear analyses in herbivorous and carnivorous mammals at the same magnification. Specifically, we compare observer-generated 2D microwear data from photosimulations of the identical scanned areas of DMTA in extant African bovids and carnivorans using a scanning white light confocal microscope at 100x magnification. Using this magnification, dental microwear features quantified in 2D were able to separate grazing and frugivorous bovids using scratch frequency; however, DMTA variables were better able to discriminate between disparate dietary niches in both carnivorous and herbivorous mammals. Further, results demonstrate significant interobserver differences in 2D microwear data, with the microwear index remaining the least variable between experienced observers, consistent with prior research. Overall, our results highlight the importance of reducing observer error and analyzing dental microwear in three dimensions in order to consistently interpret diets accurately.     

Caecal size and function in the rock elephant shrew Elephantulus myurus (Insectivora, Macroscelididae) and the Namaqua rock mouse Aethomys namaquensis (Rodentia, Muridae)

1. The relative size of the digestive organs and the function of the caeca of an insectivorous elephant shrew Elephantulus myurus (Macroscelididae) and of a herbivorous rodent Aethomys namaquensis (Muridae) were compared. 2. Both species had similar body mass but A. namaquensis had a significantly heavier total digestive tract, full stomach, and caecum and a longer large intestine and caecum than E. myurus. 3. Both species had similar total volatile fatty acid (VFA) concentration and VFA % composition although A. namaquensis had a significantly higher % of n-butyric acid. Both had a similar caecal NH3-N concentration. 4. The presence of a functional caecum in E. myurus supports the view that Macroscelididae have evolved from ancestral herbivores and not from insectivores.     

Microbiological evaluation of the intraruminal in sacculus digestion technique.

The influence of nature of the feed sample, feeding frequency and pore size on the influx of bacteria and protozoa into synthetic fiber bags suspended in the rumens of sheep fed different diets was studied. Counts of total culturable bacteria in bags with a pore size of 10 microns were less than 30% of the ruminal counts for animals that were fed the lucerne hay and high-roughage diets. The maximum count (62 and 82% of the ruminal count) for these specific diets was obtained by using bags with a pore size of 53 microns. Protozoal counts in bags with pore sizes of 30 and 53 microns were equal to or higher than the ruminal counts for the lucerne hay and high-roughage diets but less than half of the ruminal count for the low-roughage diet. An interaction between incubation time, feeding frequency of the host animals, and the microbial populations developing inside the bags was also demonstrated. The results clearly show that the microbial population inside the bag differed from that of the surrounding ruminal ingesta and that caution must be taken in interpreting results on feed evaluation and especially on rates of degradation when using the in sacculus technique. Factors influencing the influx of bacteria and protozoa into bags with different pore sizes and containing a variety of substrates are discussed together with suggestions for the use of this technique.     

Midwater macroplankton of British Columbia studied by submersible PISCES IV

Data are reported from 30 dives during winter and spring 1980–83at sites in the Strait of Georgia and inlets running off it,and in inlets on the west coast of Vancouver Island. Observationswere made from the surface to the bottom (maximum 733 m) butmost attention was given to the midwater plankton community.The vertical distribution and abundance of hydromedusae, siphonophores,ctenophores, euphausiids, pelagic worms and molluscs were recordedsystematically, along with data for one copepod species (Neocalanusplumchrus). The midwater environment was found to be stablein terms of species composition and depth ranges, which permittedthe data for several years and many locations to be pooled.Four categories of plankton are recognized: (a) epipelagic (concentratedin the top 50 m); (b) mesopelagic (50–175 m); (c) bathypelagic(below 175 m); and (d) meso-bathypelagic (forms living in bothmeso- and bathypelagic zones). Species in this last categorybehave like mesopelagic forms at the upper end of their ranges,migrating to the surface at night. Deeper-lying members of thesame species do not migrate. For six such species, the cut-offpoint between migratory and non-migratory components was foundto lie at a mean depth of 175 m. This depth is therefore takenas the demarcation point between the meso- and bathypelagiczones. Taking account of published data on light penetration,it is estimated that, for the whole region, daytime light intensityat 175 m, and hence the effective limit for phototaxis of thespecies in question, lies in the range 10^–8–10^–9µW cm^–2.     

Postoperative Depression of Tumour-directed Cell-mediated Immunity in Patients with Malignant Disease

Leucocytes from 46 melanoma patients, 45 breast carcinoma patients, and 95 control donors were tested by the leucocyte migration test against the supernatants of homogenates of malignant melanomas, breast carcinomas, simple breast tumours, and breasts showing simple cystic disease. By comparison with controls inhibition of migration occurred significantly more frequently when tumour patients'' leucocytes were exposed to extracts of histogenetically similar tumours.Cell-mediated immunity to tumour-associated antigens was measured in 12 patients with breast carcinoma and 12 with malignant melanoma immediately before surgical operation and in the postoperative period. All patients tested before operation showed significant inhibition of migration on contact with extracts of histogenetically similar tumours. Postoperatively the degree of leucocyte migration inhibition was reduced in all patients with melanoma and breast carcinoma. Significant inhibition of leucocyte migration returned in most patients 6-22 days after operation.     

Structural components of alginic acid. I. The crystalline structure of poly-beta-D-mannuronic acid. Results of x-ray diffraction and polarized infrared studies

A Structure determination of the naturally occuring marine algal polysaccharide poly-β-D -mannuronic acid is described. The structure consists of 1e → 4e linked D -mannuronic acid chains with the monosaccharide units in the C1 chair conformation. The X-ray fiber diffraction photograph obtained from bundles of fibers prepared from Fucus vesiculosus has been indexed to an orthorhombic unit cell in which a =7.6 Å, b (fiber axis) = 10.4 Å, c = 8.6 Å, the unit cell containing two disaccharide chain segments with space group P2₁2₁2₁. A sheet-like structure involving one intra-chain, one intra-sheet, and one inter-sheet hydrogen bond per monosaccharide is proposed. Features of the chain-packing arrangement are compared with mannan.     

Efficiency of bacterial protein synthesis during anaerobic degradation of cattle waste

The rate of [15N]ammonia (15NH3) uptake or incorporation into bacterial cells was studied, using stirred, 3-liter benchtop digestors fed on a semicontinuous basis with cattle waste. The fermentations were carried out at 40 and 60 degrees C and at four different loading rates (3, 6, 9, and 12 g of volatile solids per liter of reactor volume per day). The rate of NH3-N incorporation for the period 1 to 5 h after feeding at the four different loading rates was 0.49, 0.83, 1.05, and 1.08 mg/liter per h in the mesophilic digestor and 0.68, 1.07, 1.17, and 1.21 mg/liter per h in the thermophilic digestor. Values were lower 7 to 21 h after feeding in both digestors and were related to the rate of fermentation or CH4 production. In the mesophilic digestors, the rate of bacterial cell production ranged from 3.97 to 8.72 mg of dry cells per liter per h, 1 to 5 h after feeding at the different loading rates. Corresponding values for the thermophilic digestors ranged from 5.46 to 9.77 mg of dry cells per liter per h. Cell yield values ranged from 2.3 to 3.1 mg of dry cells per mol of CH4 produced in the mesophilic and thermophilic digestors at the two lower loading rates. The values were higher (2.8 to 3.4) in the mesophilic digestors at the two higher loading rates because of the accumulation of propionate and a consequent reduction in CH4 production. Low cell yields such as those measured in this study are characteristic of low-specific-growth rates under energy-limited conditions.     

Partial characterization of a DNA restriction endonuclease from Ruminococcus flavefaciens FD-1 and its inhibition by site-specific adenine methylation.

The principal DNA restriction-modification system of the cellulolytic ruminal bacterium Ruminococcus flavefaciens FD-1 is described. The restriction endonuclease RflFI could be separated from cell extracts by phosphocellulose and heparin-sepharose chromatography. Restriction enzyme digests utilizing RflFI alone or in combination with SalI, a restriction enzyme isolated from Streptomyces albus G, showed that the DNA sequence recognized by RflFI either overlapped or was the same as that recognized by SalI. DNA sequence analysis confirmed that RflFI was identical in activity to SalI, with the recognition sequence being 5'-GTCGAC-3' and cleavage occurring between G and T. Adenine methylation within this sequence can be catalyzed in vitro by TaqI methylase, and this inhibited the cleavage of plasmid DNA molecules by RflFI and SalI. Chromosomal DNA from R. flavefaciens FD-1 is also methylated within this DNA sequence because neither restriction endonuclease could degrade this DNA substrate. These findings provide a means to protect plasmid molecules from degradation prior to gene transfer experiments with R. flavefaciens FD-1.