Polymorphism of transferrin and esterase in Alaskan wolves: evidence of close molecular homology with the dog

By the use of isoelectric focusing in polyacrylamide gels serum samples from 146 Alaskan wolves were studied with regard to transferrin (Tf) and esterase (ArE) polymorphism, comparing the phenotypic band patterns with those of selected Norwegian dogs. The study revealed Tf and ArE polymorphisms in the wolf with phenotypic band patterns being indistinguishable from the corresponding ones in dogs. This suggests the occurrence of the same two common Tf alleles in the wolf as in the dog. In the ArE system the results are consistent with the occurrence of three alleles which also occur in dogs whereas a fourth allele, so far not seen in dogs, is seen in Alaskan wolves.     

Analysis of beta-hydroxy-beta-methyl butyrate in plasma by gas chromatography and mass spectrometry

A method for measuring the branched chain hydroxy acid beta-hydroxy-beta-methyl butyrate (HMB, a product of leucine catabolism) has been described. A [2H6]HMB internal standard was added to plasma and standards, and samples were extracted with diethyl ether, backextracted into neutral phosphate, dried, and derivatized for gas chromatography and mass spectrometry. The natural HMB was monitored at 175 amu and the deuterated HMB was monitored at 181 amu. Standard curves were linear to at least 25 microns and were quantitatively recovered from plasma. Basal concentrations of plasma HMB were from 1 to 2 microM in sheep and increased three- to fourfold when leucine's alpha-ketoacid (alpha-ketoisocaproate, KIC) was fed to lambs. This method can also be adapted to quantitate KIC and other branched chain ketoacids in plasma during the same run.     

Proteolysis of the heavy chain of major histocompatibility complex class I antigens by complement component C1s.

The major histocompatibility complex (MHC) class I antigens contain a light chain, beta 2-microglobulin, non-covalently associated to the transmembrane heavy alpha-chain carrying the allotypic determinants. Since the C1q complement component is known to associate with beta 2-microglobulin, and we recently found that activated C1s complement was capable of cleaving beta 2-microglobulin, we decided to investigate the proteolytic activity of C1 complement towards the heavy chain of class I antigens. Our results demonstrate that human C1s complement cleaves the heavy chain of human class I antigens into at least two fragments, with apparent molecular weights of 22,000 and 24,000 g/mol on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), under both reducing and non-reducing conditions. The cleavage of the heavy chain is inhibited by the presence of C1 esterase inhibitor. The molecular weights of the fragments are in agreement with the cleavage located in the area between the disulphide loops of the alpha 2-and alpha 3-domains of the heavy chain. In addition human C1s complement is able to cleave H-2 antigens from mouse in a similar fashion but not rat MHC class I antigen or mouse MHC class II antigen (I-Ad). Mouse MHC class I antigen-specific determinants could also be detected in supernatant from mouse spleen cells incubated with C1r and C1s. These results indicate the presence in the body fluids of a non-membrane-bound soluble form of the alpha 1-and alpha 2-domains which represent the binding site for antigenic peptides.     

Xylem Hydraulic Characteristics, Water Relations and Wood Anatomy of the Resurrection PlantMyrothamnus flabellifoliusWelw.

Myrothamnus flabellifoliusWelw. is a desiccation-tolerant (‘resurrection’)plant with a woody stem. Xylem vessels are narrow (14 µmmean diameter) and perforation plates are reticulate. This leadsto specific and leaf specific hydraulic conductivities thatare amongst the lowest recorded for angiosperms (k_s0.87 kg m^-1MPa^-1s^-1;k_l3.28x10^-5kg m^-1MPa^-1s^-1, stem diameter 3 mm). Hydraulic conductivitiesdecrease with increasing pressure gradient. Transpiration ratesin well watered plants were moderate to low, generating xylemwater potentials of -1 to -2 MPa. Acoustic emissions indicatedextensive cavitation events that were initiated at xylem waterpotentials of -2 to -3 MPa. The desiccation-tolerant natureof the tissue permits this species to survive this interruptionof the water supply. On rewatering the roots pressures thatwere developed were low (2.4 kPa). However capillary forceswere demonstrated to be adequate to account for the refillingof xylem vessels and re-establishment of hydraulic continuityeven when water was under a tension of -8 kPa. During dehydrationand rehydration cycles stems showed considerable shrinking andswelling. Unusual knob-like structures of unknown chemical compositionwere observed on the outer surface of xylem vessels. These maybe related to the ability of the stem to withstand the mechanicalstresses associated with this shrinkage and swelling.Copyright1998 Annals of Botany Company cavitation, desiccation, hydraulic conductivity, refilling, resurrection plant, root pressure, xylem anatomy,Myrothamnus flabellifolius     

Difluoromethylornithine counteracts effects of auxins and inhibitors of polar auxin transport on plant development

Difluoromethylornithine (DFMO) counteracted several processes that are promoted or inhibited by auxins or inhibitors of polar auxin transport: inhibition of asymmetric gene expression in carrot, stimulation of gametic embryogenesis inBrassica, inhibition of root elongation in tobacco, inhibition of the development of lateral roots in pea and adventitious roots in apple, and inhibition of floral bud formation inArabidopsis     

On lipid droplets in renal interstitial cells

Summary By examining Epon-sections of the renal papilla, it is demonstrated that acute hydration in dehydrated rats induces a considerable increase in the number of lipid droplets in the renal interstitial cells. It is supposed that the increase in number of lipid droplets represents a state of limited release. The attention is drawn to the correlation between the increased number of lipid droplets and the state of diuresis. The possibility of a correlation between the effect of ADH and prostaglandin and the release of lipid droplets is mentioned.This work was supported by a grant from the Danish State Research Foundation. — The author wishes to acknowledge the support and inspiration given by E. Bojesen, M.D., Ph., D., the Institute of Experimental Medicine, Division of Endocrinology.     

Characterization of Solanum tuberosum Multicystatin and Its Structural comparison with Other Cystatins

Potato (Solanum tuberosum) multicystatin (PMC) is a crystalline Cys protease inhibitor present in the subphellogen layer of potato tubers. It consists of eight tandem domains of similar size and sequence. Our in vitro results showed that the pH/PO₄⁻-dependent oligomeric behavior of PMC was due to its multidomain nature and was not a characteristic of the individual domains. Using a single domain of PMC, which still maintains inhibitor activity, we identified a target protein of PMC, a putative Cys protease. In addition, our crystal structure of a representative repeating unit of PMC, PMC-2, showed structural similarity to both type I and type II cystatins. The N-terminal trunk, α-helix, and L2 region of PMC-2 were most similar to those of type I cystatins, while the conformation of L1 more closely resembled that of type II cystatins. The structure of PMC-2 was most similar to the intensely sweet protein monellin from Dioscorephyllum cumminisii (serendipity berry), despite a low level of sequence similarity. We present a model for the possible molecular organization of the eight inhibitory domains in crystalline PMC. The unique molecular properties of the oligomeric PMC crystal are discussed in relation to its potential function in regulating the activity of proteases in potato tubers.