Amylase heterogeneity variants in man

The existence of six amylase heterogeneity variants in serum and urine has been discovered in a group of 111 families with twins, and the frequence of each variant was determined. It had been shown that each of these amylase heterogeneity variants is inherited codominantly, and the mode of inheritance is demonstrated schematically.These amylase heterogeneity variants may be used as an aid to twin zygosity determination and also in paternity problems.     

Physiological properties of newly formed synapses between sympathetic preganglionic neurons and sympathetic ganglion neurons

We have examined the physiological properties of transmission at newly formed synapses between sympathetic preganglionic neurons and sympathetic ganglion neurons in vitro. Chick neurons were labeled with fluorescent carbocyanine dyes before they were placed into culture (Honig and Hume, 1986), and were studied by making intracellular recordings during the first 2 weeks of coculture. Evoked monosynaptic excitatory postsynaptic potentials (EPSPs) were not observed until 48 h of coculture. Beyond this time, the frequency with which connected pairs could be found did not vary greatly with time. With repetitive stimulation, the evoked monosynaptic EPSPs fluctuated in amplitude from trial to trial and showed depression at frequencies as low as 1 Hz. To gain further information about the quantitative properties of transmission at newly formed synapses, we analyzed the pattern of fluctuations of delayed release EPSPs. In mature systems, delayed release EPSPs are known to represent responses to single quanta, or to the synchronous release of a small number of quanta. For more than half of the connections we studied, the histograms of delayed release EPSPs were extremely broad. This result suggested that either quantal reponses are drawn from a continuous distribution that has a large coefficient of variation or that there are several distinct size classes of quantal responses. The pattern of fluctuation of monosynaptic EPSPs was consistent with both of these possibilities, and was inconsistent with the possibility that monosynaptic EPSPs are composed of quantal subunits with very little intrinsic variation. Although variation in the size of responses to single quanta might arise in a number of ways, one attractive explanation for our results is that the density and type of acetylcholine receptors varies among the different synaptic sites on the surface of developing sympathetic ganglion neurons.     

Characterization of the eaeA gene from rabbit enteropathogenic Escherichia coli strain RDEC-1 and comparison to other eaeA genes from bacteria that cause attaching-effacing lesions

Abstract A number of enteric pathogens, including enteropathogenic (EPEC) and enterohemorrhagic (EHEC) Escherichia coli , Hafnia alvei , a strain of Citrobacter freundii , and rabbit EPEC strain RDEC-1 cause attaching-effacing (AE) lesions in the gut mucosa. These bacteria have a pathogenicity cassette (locus of enterocyte effacement or LEE) containing the eaeA gene. This gene encodes intimin, an outer membrane protein required for production of AE lesions. RDEC-1, a non-invasive enteropathogen in young rabbits, produces AE lesions morphologically indistinguishable from lesions caused by human AE bacterial strains. The RDEC-1 example of E. coli diarrhea in rabbits is an important model for studying the pathogenesis of AE bacteria in a natural infection and for analyzing specific roles of the components of LEE. In order to better understand the role of intimin in the development of AE lesions, a portion of DNA within RDEC-1 LEE, containing the eaeA gene and an upstream open reading frame (ORF), was sequenced. The RDEC-1 eaeA gene shared 87%, 92%, and 93% DNA sequence identity and > 80% amino acid sequence identity with the eaeA genes of C. freundii biotype 4280, EHEC O157:H7, and EPEC O127:H6, respectively. The carboxy-terminal 280 amino acid residues of intimin has 80%, 56%, and 54% identity with C. freundii , EHEC O157:H7, and EPEC O127:H6 intimins, respectively. The predicted protein encoded by the upstream ORF (156 amino acids) shares 95%, 97%, and 99% amino acid identity with predicted proteins from C. freundii , EHEC O157:H7, and EPEC O127:H6, respectively. The high degree of sequence homology of the ORF and the eaeA gene of RDEC-1 with those of other AE bacteria suggests an evolutionary relationship of LEE and supports and facilitates the use of the RDEC-1 model for studying the role of LEE in pathogenesis.     

Characterization of Mhc genes in a multigenerational family of ring-necked pheasants

Little is known about the major histocompatibility (Mhc) genes of birds in different taxonomic groups or about how Mhc genes may be organized in avian species divergent by evolution or habitat. Yet it seems likely that much might be learned from birds about the evolution, organization, and function of this intricate complex of polymorphic genes. In this study a close relative of the chicken, the ring-necked pheasant (Phasianus colchicus), was examined for the presence and organization of Mhc B-G genes. The patterns of restriction fragments revealed by chicken B-G probes in Southern hybridizations and the patterns of pheasant erythrocyte polypeptides revealed in immunoblots by antisera raised against chicken B-G polypeptides provide genetic, molecular, and biochemical data confirming earlier serological evidence for the presence of B-G genes in the pheasant, and hence, the presence of a family of B-G genes in at least a second species of birds. The high polymorphism exhibited by the pheasant B-G gene family allowed genetic differences among individuals within the small experimental population in this study to be detected easily by restriction fragment patterns. Further evidence was found for the organization of the pheasant Mhc class I and class II genes into genetically independent clusters. Whether these gene clusters are fully comparable to the B and Rfp-Y systems in the chicken or whether yet another organization of Mhc genes has been encountered in the pheasant remains to be determined.     

Genetic differentiation between Carex lasiocarpa and C. Pellita (Cyperaceae) in north america

Carex lasiocarpa and C. pellita (sect. Carex) share a very similar morphology and have overlapping ranges in North America, but are found in different habitats characterized by contrasting soil types and pH. We studied allozyme variation and chromosome numbers to assess genetic differentiation between the two taxa. Both principal components analysis on the allele frequencies from 12 putative enzyme-coding loci and cluster analysis of genetic identities separated 51 sampled populations into two groups that were consistent with recognized structural differences between C. lasiocarpa and C. pellita. Mean within-group genetic identities were 0.95 for C. lasiocarpa and 0.93 for C. pellita; mean between-group genetic identity was 0.81. With the exception of two rare alleles, the alleles of C. pellita were a subset of those found in C. lasiocarpa. Principal components analysis of measurements of structural characters from voucher specimens representing 46 populations also separated the two species with minimal overlap. Meiotic squashes of microsporocytes revealed haploid chromosome numbers of 38 and 38 + 1 for C. lasiocarpa and 41 and 40 + 1 for C. pellita. These data support the continued recognition of the two taxa as distinct species, and suggest that C. pellita may be a daughter species still in the process of divergence from C. lasiocarpa.     

Feeding ecology of phaeodarian radiolarians at the VERTEX North Pacific time series site

Feeding ecology of five species of phaeodarians was analyzedusing samples collected in a timeseries of sediment trap deploymentsfrom October 1986-May 1988 from 100–2000 m at an oligotrophicnorth Pacific site. Quantitative analysis using transmissionelectron microscopy of contents of feeding vacuoles showed thatheterotrophic flagellates and eukaryotic algae followed by bacteria,and then prokaryotic algae, constituted the largest volumesof recognizable organisms consumed throughout the depth rangesampled. Phaeodarians were predominantly generalists, appearedto feed on sinking organic aggregates, and may select eukaryotesover higher biomass bacteria. Other than a decrease in totalrecognizable cells with increasing depth, few seasonal or depthpatterns in consumed food occurred in this oligotrophic environment.Vacuole contents of co-occurring species showed no evidenceof food resource partitioning. The trophic role of phaeodariansis that of consumers of small eukaryotes and prokaryotes andrepackages of detritus throughout the water column. ³Present address: Electron Microscope Laboratory, 26 GianniniHall, University of California, Berkeley, CA 94720, USA     

Interaction of trace elements in a longitudinal study of human milk from full-term and preterm mothers

Concentrations of 8 trace elements (Fe, Cu, Zn, Se, Br, Pb, Rb, and Sr) at different lactation time were measured by the PIXE multi-elemental technique. Time dependence and interelement correlations were studied. A total of 200 milk samples from 32 lactating mothers were supplied from 2 to 120 d after delivery of 26 full-term and 6 preterm infants. All elements showed a lognormal frequency-distribution. The Fe, Cu, Zn, and Se contents in preterm milk were found to be somewhat different with respect to full-term milk. Cu, Zn, Se, Br, Pb, and Rb concentrations declined with lactation time, both in pre- and full-term samples. Sr and Fe contents did not show any change with time. Detailed analysis of data by partial correlation and multiple regression methods was performed. No substantial differences between preterm and full-term samples were found in the results of partial correlation analysis. Cu and Zn were found to be correlated with lactation time, whereas the measured time dependence for the other elements has to be attributed to the effect of the existing interelement correlation. All the measured elements appeared to be correlated with at least one other element. In particular, Se was inversely correlated with Zn and directly with Cu. The zinc and copper contents in milk can therefore depend on the variation in the mother selenium intake.