Development and structure of the pericarp of Lannea discolor (Sonder) Engl.(Anacardiaceae)

Development and structure of the pericarp of Lannea discolor (Sonder) Engl.(Anacardiaceae). The exocarp develops from the outer epidermis and subepidermal, parenchymatous cell layers of the ovary wall. A parenchymatous zone with secretory cavities more or less delimits the exocarp internally. The inner part of the parenchymatous mesocarp is tanniniferous. The parenchymatous transition zone between mesocarp and sclercnchymatous endocarp or sderocarp, contains vascular tissue. The inner endocarp and operculum develop from the inner epidermis and subepidermal parenchyma of the ovary wall, while the outer endocarp develops from the parenchymatous zone with procambium strandS. Comparing the pericarp of L.discolor with those of Sclerocarya birrea subsp. caffra and Rhus lancea , the close affinity with Sclerocarya birrea subsp. caffra is evident.     

The rabbit alpha-like globin gene cluster is polymorphic both in the sizes of BamHI fragments and in the numbers of duplicated sets of genes

The alpha-like globin gene cluster in rabbits contains embryonic zeta- globin genes, an adult alpha-globin gene, and theta-globin genes of undetermined function. The basic arrangement of genes, deduced from analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3'. However, the pattern of restriction fragments containing zeta- and theta-globin genes varies among individual rabbits. Analysis of BamHI fragments of genomic DNA from 24 New Zealand white rabbits revealed eight different patterns of fragments containing zeta-globin genes. The large BamHI fragments containing genes zeta 0 and zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary in size. In contrast to this constancy in the size of the restriction fragments, the copy number of the zeta 2 and zeta 3 genes does vary among different rabbits. No length polymorphism was detected in the BamHI fragments containing the theta-globin genes, but again the copy number varies for restriction fragments containing the theta 2 gene. The alpha 1- and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI fragment. The combined data from hybridization with both zeta and theta probes shows that the BamHI cleavage pattern does not vary within the region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern genomic blot-hybridization patterns for the progeny of parental rabbits with different zeta-globin gene patterns shows that the polymorphic patterns are inherited in a Mendelian fashion. Two different haplotypes have been mapped based on the genomic blot-hybridization data. The variation in the alpha-like globin gene cluster in the rabbit population results both from differences in the copy number of the duplication block containing the zeta-zeta-theta gene set and from the presence or absence of polymorphic BamHI sites.      

Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution

In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.      

Pacemaker Properties of Completely Isolated Neurones in <Emphasis Type="Italic">Aplysia californica</Emphasis>

SINGLE-CELL pacemaker activity is interesting because of its function in temporal organization and information processing in the nervous system. Many invertebrate neurones are regularly and autonomously active^1,2. Although the pacemaker rhythm probably originates within the recorded neurone, it is not clear whether it originates in the axonal tree or in the cell soma. Alving³ approached this question by studying pacemaker activity in the soma of Aplysia nerve cells, after ligaturing the axonal stem with fine sutures. The study described here presents evidence that nerve cell somata which are completely dissociated from all surrounding tissue and with or without axons, are able to maintain regular autorhythmic activity for periods of more than 24 h. The method of complete isolation of cells represents some progress over Alving's method because it is easier to accomplish, has a larger yield of viable neurones and allows longer recording periods.     

UEBER EINE NEUE FOSSILE REPTILFORM VON PROVINZ HUPEH,CHINA

Das zur Untersuchung vorliegende Exemplar wurde von einer geologischen Expedition derProvinz Hupeh in Nanchang-Distrikt in 1956 gefunden und übergeliefert.Der Erhaltungszustand dieses Exemplares ist wie folgende:Gut erhaltende Teile sind dieOberfl(?)che des hinteren Teils des Sch(?)dels,Hals-und Rumpf-Wirbel und-Rippen.Die mitteleund vordere Teile des Sch(?)dels sind abgerieben.Der Unterkiefer ist nicht erhalten.Der vordere     

Eimeria carolinensis n. sp., a Coccidium from the White-Footed Mouse, Peromyscus leucopus (Rafinesque)

SYNOPSIS. Eimeria carolinensis n.sp. (Sporozoa) is described from oöcysts in the feces of the white-footed mouse, Peromyscus leucopus (Rafinesque) taken in the vicinity of Durham, North Carolina. The oöcysts are ellipsoidal to elongate ellipsoidal, 14–19.5 × 10–13 μ, mean of 17.6 × 11.3 μ. Micropyle absent. Oöcyst wall composed of 2 layers. A refractile granule present but no oöcyst residuum. Sporocysts ovoid almost filling the oöcyst. Small Stieda body present.