Prairie plant guilds: a multivariate analysis of prairie species based on ecological and morphological traits

An ecomorphological analysis of the tallgrass prairie of central North America divided representative species of the native grassland flora into eight guilds or groups of species with similar life-form, phenology, and ecology. The guilds, segregated by multivariate analysis, are: (1) warm-season graminoids with Kranz anatomy and the Hatch-Slack photosynthetic pathway (C4 grasses); (2) cool-season graminoids without Kranz anatomy, but with the common Calvin or C3 photosynthetic pathway (C3 grasses and sedges); (3) annuals and biennial forbs; (4) ephemeral spring forbs; (5) spring forbs; (6) summer/fall forbs; (7) legumes; and (8) woody shrubs. The study was based on 158 plant species indigenous to three upland prairie sites in northeastern Kansas. Each species was scored for 32 traits which fall into five broad categories: plant habit, leaf characteristics, stem structures, root structures, and reproductive traits, including phenology. A multivariate, detrended correspondence analysis sorted the 158 species into the eight principal groups or guilds. These groups were further supported by a cluster analysis and discriminant function analysis of the same data set. The discriminant function analysis determined that 94.3% of the species were correctly classified in their respective guilds, and that the guilds were statistically different. Results indicate that guild analysis offers a basis for detailed classification of grassland vegetation that is more ecologically focused than species composition, as the myriad of species (about 1,000 prairie species on the central plains of North America) vary in presence, cover, and importance with their individualistic distribution.Abbreviations C3= C3 photosynthesis - C4= C4 photosynthesis - LSD= least significant difference     

A novel human type I hair keratin gene: evidence for two keratin hHa3 isoforms

We present the nucleotide and amino acid sequence for a novel human type I hair keratin, which could be identified through its high sequence homology and strict carboxyterminal length identity as a human ortholog of the murine hair keratin mHa3. Our hHa3 sequence differs, however, from that of a previously described hHa3 hair keratin (published only as an amino acid sequence; [13]) in 24 amino acid positions, 8 of which occur in the middle of the carboxyterminal domain. PCR of genomic DNA from 25 normal human subjects using a primer pair derived from sequence segments located in the 3-region of our hHa3 clone that encode conserved amino acid sequences in both keratins, resulted in the amplification of two distinct products of 0.38 kbp and 1.0 kbp. DNA sequence analysis of the cloned PCR products allowed identification of the 0.38 kb sequence as that originating from Yuet al. [13] and the 1.0 kb sequence as that being derived from our data. The difference in fragment length was due to unique intron 6 sequences, indicating that these two keratin species are encoded by genes of their own. Moreover, extensive Southern blot analyses with DNA from 25 unrelated individuals of different races using a 3-noncoding sequence from our keratin and the intron 6 sequence of the keratin of Yuet al. [13], as hybridization probes showed that both keratin genes are present as single copy sequences occurring ubiquitously and without gross alterations in the human genome. Collectively, these data demonstrate that the human type I hair keratin described in this paper represents an isoform of the previously described hHa3 keratin. We propose that these hHa3 isoforms be named in chronological order of discovery hHa3-I and hHa3-II.     

Chemotaxonomic value of anthocyanins in Podalyria and Virgilia (tribe Podalyrieae: Fabaceae)

Anthocyanin pigments responsible for purple and pink flower colours in the tribe Podalyrieae have been identified. The considerable variation in flower colour is not reflected in the chemical variation and the flower pigments are surprisingly conservative. Virgilia flowers always have the acetic acid esters of cyanidin-3-glucoside and peonidin-3-glucoside as major compounds, together with trace amounts of the coumaroyl ester of cyanidin-3-glucoside. Podalyria flowers invariably have the rather more stable coumaroyl ester of cyanidin. The data support a close affinity between the two genera but also show that flower colour is only partially homologous.     

Inhibition of G1 phase cyclin dependent kinases by transforming growth factor β1

Transforming growth factor β1 (TGFβ1) inhibits epithelial cell proliferation late in the G1 phase of the cell cycle. We examined the effect of TGFβ1 on known late G1 cell cycle regulators in an attempt to determine the molecular mechanism of growth inhibition by this physiological inhibitor. The results demonstrate the TGFβ1 inhibits the late G1 and S phase specific histone H1 kinase activity of p33^cdk2. This inhibitiion is not dur to TGFβ1's effect on p33^cdk2 synthesis, but rather due to its negative effect on the late G1 phosphorylation of p33^cdk2. It is also shown that TGFβ1 inhibits both late G1 cyclin A and cyclin E associated histon H1 kinase activities. The inhibitor has no effects on the synthesis of cyclin E but to inhibit the synthesis of cyclin A protein in a cell cycle dependent manner. If TGFβ1 is added to cells which have progressed futher than 8 hours into G1, then it is without inhibitory effect on cyclin A synthesis. These effect on TGFβ1 on late G1 cell cycle regulators correlate well with its inhibitory effects on cellular growth and suggest that these G1 cyclin dependent kinases might serve as targets for TGFβ1-mediated growth arrest.     

Variation among early Homo crania from Olduvai Gorge and the Koobi Fora region

Fossils recognized as early Homo were discovered first at Olduvai Gorge in 1959 and 1960. Teeth, skull parts and hand bones representing three individuals were found in Bed I, and more material followed from Bed I and lower Bed II. By 1964, L.S.B. Leakey, P.V. Tobias, and J.R. Napier were ready to name Homo habilis. But almost as soon as they had, there was confusion over the hypodigm of the new species. Tobias himself suggested that OH 13 resembles Homo erectus from Java, and he noted that OH 16 has teeth as large as those of Australopithecus. By the early 1970s, however, Tobias had put these thoughts behind him and returned to the opinion that all of the Olduvai remains are Homo habilis. At about this time, important discoveries began to flow from the Koobi Fora region in Kenya. To most observers, crania such as KNM-ER 1470 confirmed the presence of Homo in East Africa at an early date. Some of the other specimens were problematical. A.C. Walker and R.E. Leakey raised the possibility that larger skulls including KNM-ER 1470 differ significantly from smaller-brained, small-toothed individuals such as KNM-ER 1813. Other workers emphasized that there are differences of shape as well as size among the hominids from Koobi Fora. There is now substantial support for the view that in the Turkana and perhaps also in the Olduvai assemblages, there is more variation than would be expected among male and female conspecifics. One way to approach this question of sorting would be to compare all of the new fossils against the original material from Olduvai which was used to characterize Homo habilis in 1964. A problem is that the Olduvai remains are fragmentary, and none of them provides much information about vault form or facial structure. An alternative is to work first with the better crania, even if these are from other sites. I have elected to treat KNM-ER 1470 and KNM-ER 1813 as key individuals. Comparisons are based on discrete anatomy and measurements. Metric results are displayed with ratio diagrams, by which similarity in proportions for several skulls can be assessed in respect to a single specimen selected as a standard. Crania from Olduvai examined in this way are generally smaller than KNM-ER 1470, although OH 7 has a relatively long parietal. In the Koobi Fora assemblage, there is variation in brow thickness, frontal flattening and parietal shape relative to KNM-ER 1470. These comparisons are instructive, but vault proportions do not help much with the sorting process. Contrasts in the face are much more striking. Measurements treated in ratio diagrams show that both KNM-ER 1813 and OH 24 have relatively short faces with low cheek bones, small orbits and low nasal openings. Also, they display more projection of the midfacial region, just below the nose. This is not readily interpreted to be a female characteristic, since in most hominoid primates the females tend to have flatter lower faces than the males. The obvious size differences among these individuals have usually been interpreted as sex dimorphism, but, in fact, two taxa may be sampled at Olduvai and in the Turkana basin at the beginning of the Pleistocene. One large-brained group made up of KNM-ER 1470, several other Koobi Fora specimens, and probably OH 7, can be called Homo habilis. If these skulls go with femora such as KNM-ER 1481 and the KNM-ER3228 hip, then this species is close in postcranial anatomy to Homo erectus. The other taxon, including small-brained individuals such as KNM-ER 1813 and probably OH 13, seems also to be Homo rather than Australopithecus. If the OH 62 skeleton is part of this assemblage, then the small hominids have postcranial proportions unlike those of Homo erectus. However, it is too early to point unequivocally to one or the other of these groups as the ancestors of later humans. Both differ from Homo erectus in important ways, and both need to be better understood before we can map the earliest history of the Homo clade. © 1993 Wiley-Liss, Inc.     

Insect herbivory on water mint: you can't get there from here?

Aquatic plants are thought to have fewer herbivore species than their terrestinal counterparts, and possibly to suffer less herbivory I examined herbivory on water mint Mentha aquatica growing in and out of water and tested possible processes determining the observed pattern of leaf damage Plants growing on land had much more herbivore damage than those growing in water The most common herbivore of Mentha at the site (a chrysomelid beetle) showed no p reference for leaves from terrestrial plants over those from aquatic plants Caging aquatic plants to exclude moorhens suggested that these predators were not having a strong effect in removing insect herbivores (though this conclusion is tentative due to low insect numbers) Transplanting aquatic plants to a terrestrial location, while keeping their roots in water, resulted in marked increases in herbivore damage, relative to control aquatic plants The results suggest that the water barrier may prevent effective exploitation of emergent aquatic plants by terrestrial herbivores This may have consequences for observed patterns of herbivore richness on such plants, plant fitness, and a more speculative suggestion, for the mode of reproduction in aquatic plants     

Substance P in the suprachiasmatic nucleus of the rat: an immunohistochemical and in situ hybridization study

Using a biotin-streptavidin-horseradish peroxidase (HRP) immunohistochemical technique the distribution of substance P-immunoreactive neuronal elements was investigated in the rat suprachiasmatic nucleus (SCN). Substance P-immunoreactive nerve fibres and varicosities were distributed throughout the suprachiasmatic nucleus, with the largest accumulation in its ventral part. Because this location overlaps with the innervation of retinal afferents, the distribution and density of substance P-immunoreactive fibres in bilaterally enucleated rats were compared to normal rats. The density of substance P-immunoreactive fibres and nerve terminals in the ventral part of the suprachiasmatic nuclei was reduced in the rats with bilateral destruction of the optic nerves, whereas the density of fibres and nerve terminals in the dorsal part as well as other retinal target areas in the thalamus and mesencephalon was unaffected. In rats pretreated with an intraventricular injection of colchicine several substance P-immunoreactive perikarya were identified in the suprachiasmatic nucleus. The immunoreactive neurons, measuring 9.7 m±1.1 m in diameter, were frequently observed in the central core of the nucleus and to a lesser extent in the dorsomedial and ventrolateral subparts. Using in situ hybridization histochemistry pre-protachykinin-A mRNA was found in the same part of the SCN indicating that synthesis of substance P takes place in SCN neurons. Using a double immunohistochemical approach applying diaminobenzidine and benzidinedihydrochloride as chromagens substance P-, vasoactive intestinal peptide (VIP)-, and vasopressin/neurophysin-immunoreactivities were identified in the same brain section. The substance P-immunoreactive perikarya constituted a separate population of SCN neurons, which were not vasopressin-, neurophysin- or VIP-immunoreactive. Taken together, these observations show that substance P is contained in the retinohypothalamic pathway and within a group of SCN cell bodies, indiating that substance P may play a role in the generation and entrainment of circadian rhythmicity.     

Developmental changes in the activity and cellular localization of hepatic casein kinase II in the rat

Abstract The activity and cellular localization of hepatic casein kinase II(CKII) was examined during late fetal development in the rat. Cultured fetal hepatocytes displayed constitutive CKII activity which was not further activated by growth factor exposure. Similarly, fetal liver CKII showed approximately fivefold greater activity than adult liver. The fetal hepatic activity was, to a large degree, localized to a nuclear fraction. Postnuclear cytosol preparations from fetal and adult liver showed similar CKII activity. In all cases, FPLC ion exchange chromatography followed by Western immunoblotting showed that immunoreactive CKII coincided with kinase activity. However, Parallel determinations of CKII activity and immunoreactive CKII levels showed a higher(five-to sixfold) CKII specific activity in nuclear extracts compared to cytosol. In summary, fetal hepatic CKII demonstrates coincident nuclear localization and activation. We hypothesize that the regulation of hepatic CKII is relevant to the mitogen-independent proliferation displayed by fetal rat hepatocytes. © Wiley-Liss, Inc.     

DNA binding properties of the Saccharomyces cerevisiae DAT1 gene product.

The DAT1 gene of Saccharomyces cerevisiae encodes a DNA binding protein (Dat1p) that specifically recognizes the minor groove of non-alternating oligo(A).oligo(T) tracts. Sequence-specific recognition requires arginine residues found within three perfectly repeated pentads (G-R-K-P-G) of the Dat1p DNA binding domain [Reardon, B. J., Winters, R. S., Gordon, D., and Winter, E. (1993) Proc. Natl. Acad. Sci. USA 90, 11327-1131]. This report describes a rapid and simple method for purifying the Dat1p DNA binding domain and the biochemical characterization of its interaction with oligo(A).oligo(T) tracts. Oligonucleotide binding experiments and the characterization of yeast genomic Dat1p binding sites show that Dat1p specifically binds to any 11 base sequence in which 10 bases conform to an oligo(A).oligo(T) tract. Binding studies of different sized Dat1p derivatives show that the Dat1p DNA binding domain can function as a monomer. Competition DNA binding assays using poly(I).poly(C), demonstrate that the minor groove oligo(A).oligo(T) constituents are not sufficient for high specificity DNA binding. These data constrain the possible models for Dat1p/oligo(A).oligo(T) complexes, suggest that the DNA binding domain is in an extended structure when complexed to its cognate DNA, and show that Dat1p binding sites are more prevalent than previously thought.