Aerobic and anaerobic swimming speeds of spermatozoa investigated by twin beam laser velocimetry.

The motility of bovine and ovine spermatozoa has been studied under aerobic and anaerobic conditions, using a dual beam laser velocimeter. Cells swimming under aerobic conditions were found to be characterized by a translational swimming speed and a rotation rate that were approximately double those of cells swimming in an anaerobic environment. Both types of spermatozoa have been found to exhibit a sudden coordinated transition between fast and slow swimming states when the available oxygen is exhausted. This transition from aerobic to anaerobic swimming states has also been shown to be reversible. Studies of the duration of aerobic motility using the same apparatus have shown that the cells have a constant motile efficiency over the temperature range 32 degrees-42 degrees C.     

Oligonucleotide probes for the detection of TEM-1 and TEM-2 beta-lactamase genes and their transposons

We describe the use of molecular probes to detect the TEM-type beta-lactamase genes. As a general probe, we prepared a 656 base pair restriction fragment, entirely within the TEM structural gene. This probe was specific for the TEM family, hybridizing only with TEM-1 and TEM-2. The TEM-1 and TEM-2 beta-lactamases differ by only one amino acid. We synthesized two oligonucleotides whose central bases correspond to this difference. The use of these oligonucleotides enables us to discriminate between TEM-1 and TEM-2 genes. Using oligonucleotides homologous to parts of Tn3, we also monitored the presence of TnA-like transposons in bacteria harboring different beta-lactamase genes. Only the TEM-1 and TEM-2 genes were found to be on transposons with terminal sequences identical to those of Tn3. All hybridization experiments were performed with both dot-blot and colony-hybridization techniques, and the suitability of these two methods for epidemiological studies is compared.     

Responses of wild plants to nitrate availability

Summary Two annual species of Bromus, an invader (B. hordeaceus, ex B. mollis) and a non-invader (B. intermedius), were grown for 28 days in growth chambers, at 5 and 100 M NO ₃ ^- in flowing nutrient solution. No differences between the two species were observed at either NO ₃ ^- level, in terms of relative growth rate (RGR) or its components, dry matter partitioning, specific NO ₃ ^- absorption rate, nitrogen concentration, and other characteristics of NO ₃ ^- uptake and photosynthesis. The effects of decreasing NO ₃ ^- concentration in the solution were mainly to decrease the NO ₃ ^- concentration in the plants through decreased absorption rate, and to decrease the leaf area ratio through increased specific leaf mass and decreased leaf mass ratio. Organic nitrogen concentration varied little between the two treatments, which may be the reason why photosynthetic rates were not altered. Consequently, RGR was only slightly decreased in the 5-M treatment compared to the 100-M treatment. This is in contrast with other species, where growth is reduced at much higher NO ₃ ^- concentrations. These discrepancies may be related to differences in RGR, since a log-linear relationship was found between RGR and the NO ₃ ^- concentration at which growth is first reduced. In addition, a strong linear relationship was found between the RGR of these species and their maximum absorption rate for nitrate, suggesting that the growth of species with low maximum RGR may be partly regulated by nutrient uptake.     

Ultrasonographic determination of ovarian follicular. Development in superovulated heifers pretreated with FSH-P at the beginning of the estrous cycle

On Day 3 of the estrous cycle (estrus = Day 0), dairy heifers were given either 10 mg i.m. FSH-P (FSH-P primed; n = 9) or a saline vehicle (saline primed; n = 9). On Day 10, all heifers were superovulated with FSH-P (total = 27.7 mg i.m.) in declining doses over 5 d. Heifers were inseminated artificially at estrus. From Day 2 until estrus, the number and size of follicles >2 mm were monitored daily by ultrasonography. The mean (+/- SEM) number of corpora lutea (CL) (6.2 +/- 1.5 vs 10.7 +/- 0.9; P<0.05) and the mean number of recovered embryos and unfertilized ova (3.6 +/- 1.7 vs 8.4 +/- 2.2; P<0.05) were lower in FSH-P-primed than in saline-primed heifers. Prior to initiation of superovulation, follicles >10 mm appeared on Days 6 to 7 in saline-primed heifers but only on Days 8 to 10 in FSH-P-primed heifers (P<0.05). Also, until Day 10, the mean number of follicles 4 to 6 mm and 7 to 10 mm was higher (P<0.05) in FSH-P-primed than in saline-primed heifers. After initiation of the superovulatory treatment (Day 10 to estrus), saline-primed heifers had a greater and faster increase in the mean number of follicles >10 mm (P<0.02) than FSH-P-primed heifers did. Depletion in the number of follicles 2 to 3 mm (P<0.001) between Day 10 and estrus and in the number of follicles 4 to 6 mm (P<0.05) between Day 12 and estrus occurred in both groups of heifers. Decreased superovulatory response and embryo recovery in FSH-P-primed heifers may have been due to the presence of large follicles (>10 mm) prior to the initiation of the superovulatory treatment which reduced the ability of small follicles to grow into larger size classes during superovulatory treatment.     

Evolution of the immunoglobulin heavy chain variable region (Igh-V) locus in the genusMus

The evolution of the mouse immunoglobulin heavy chain variable region (Igh-V) locus was investigated by the comprehensive analysis of variable region (Vh) gene family content and restriction fragment polymorphism in the genusMus. The examination of naturalMus domesticus populations suggests an important role for recombination in the generation of the considerable restriction fragment polymorphism found at theIgh-V locus. Although the sizes of individualVh gene families vary widely both within and between differentMus species, evolutionary trends ofVh gene family copy number are revealed by the analysis of homologues of mouseVh gene families inRattus andPeromyscus. Processes of duplication, deletion, and sequence divergence all contribute to the evolution ofVh gene copy number. CertainVh gene families have expanded or contracted differently in the various muroid lineages examined. Collectively, these findings suggest that the evolution of individualVh family size is not driven by strong selective pressure but is relatively neutral, and that gene flow, rather than selection, serves to maintain the high level of restriction fragment polymorphism seen inM. domesticus.     

Viability of an ectomycorrhizal fungus during cross-flow filtration

Factors affecting the viability and infectivity of an ectomycorrhizal fungus during moderate concentration by cross-flow filtration were determined. Mycelial suspensions were concentrated with three commercial membrane filters (Prostak Millipore Co., M14 Tech-Sep Co. and Ceraflo Norton Co.) under aseptic conditions. Medium components may reduce the filtration rate due to their low solubility. An antifoam agent did not reduce the average flux rates as much as did the malt extract. Clear unobstructed channels (I.D. 6mm) of the tubular modules (Tech-Sep) gave the best results both in terms of performance (filtration rate) and cell viability. Shear stresses caused by pumping and flow through narrow retentate channels were probably responsible for lowering viability and infectivity. There was no linear relationship between permeate fluxes and cell concentration. There is an optimum pore size both in terms of performance (filtration rate) and cell viability. Physical blockage of large pores by hyphae could explain lower permeate flux rates than those obtained with lower pore sizes membranes.     

Nucleotide and deduced amino acid sequence of the hydrophobic surfactant protein SP-C from rat: expression in alveolar type II cells and homology with SP-C from other species

Pulmonary surfactant lowers surface tension in the lung. Its deficiency leads to the severe physiologic abnormalities seen in the respiratory distress syndrome. The hydrophobic surfactant proteins, SP-B and SP-C, appear to be especially important in the surface-spreading characteristics of pulmonary surfactant. We report the nucleotide sequence of cDNA clones for rat SP-C and compare the deduced amino acid sequence for SP-C from several species. A highly conserved domain exists within the confines of mature human SP-C. An Eisenberg plot of this region predicts a membrane-associated helix. We also demonstrate by Northern analysis the tissue-specific expression of SP-C. A comparison of signal strength between total lung RNA and RNA derived from isolated type II cells supports the idea that most SP-C messenger RNA in total lung can be accounted for by that present in alveolar type II cells.     

Preliminary assignments of the aromatic and some methyl group resonances of the 1H-NMR spectrum of the oxidized form of uteroglobin. Application to the interaction of oxidized uteroglobin with progesterone

Two-dimensional NMR methods have been used to assign aromatic and methyl group resonances in the 1H-NMR spectrum of oxidized uteroglobin. Assignments to specific amino acids are based on X-ray-determined structures of two crystal forms (C222(1) and P2(1] and on an energy-minimized X-ray structure of the C222(1) form of uteroglobin. These preliminary assignments are sufficient to probe the interaction of oxidized uteroglobin with progesterone in solution. The protein global structure is unmodified but some direct or indirect conformational changes are induced in the H1H4(H1'H4') pockets and close to Phe28 by progesterone.