Proluminal movement of 3H-androgen across the epididymal epithelium in the rat after hypophysectomy and gonadotropin supplementation

The effects of hypophysectomy and gonadotropin replacement on transepithelial movement of 3H-androgen in the rat epididymis were examined by in vivo microperifusion of 3H-testosterone followed by in vivo micropuncture to obtain peritubular and intraluminal fluid. In the caput epididymidis of normal rats, intraluminal 3H-androgen concentrations were approximately 300% of those in the interstitial space. In contrast, proluminal movement of 3H-androgen into rat caput epididymal tubules was significantly decreased 10 days after hypophysectomy. 3H-Testosterone movement across the caput epididymal epithelium was completely returned to normal by supplementation with 24 micrograms/day follicle-stimulating hormone (FSH) or 24 micrograms/day luteinizing hormone (LH). However, neither 0.12 micrograms/day FSH nor 250 micrograms/day prolactin returned proluminal androgen movement to normal. It is speculated that epididymal uptake of peritubular testosterone is mediated by androgen-binding protein, which is known to be secreted by Sertoli cells after stimulation by FSH or testosterone.     

Characterization of the muscarinic cholinergic receptor in the opossum (Didelphis virginiana, Kerr) submandibular gland: differences in receptor density and subtype compared with higher mammalian species

1. Kinetic, saturation and inhibition radioligand binding experiments with [3H]-N-methylscopolamine and [3H]quinuclidinyl benzilate were used to characterize the muscarinic cholinergic receptor in opossum (Didelphis virginiana, Kerr) submandibular salivary gland membranes. 2. The receptor density in opossum submandibular gland was found to be more than 3-fold higher than in rat, and 22-fold higher than in human, submandibular glands. 3. Inhibitor equilibrium dissociation constants for the antagonists pirenzepine, dicyclomine, atropine, N-methylscopolamine and AF-DX 116 revealed that the muscarinic receptor present in opossum submandibular gland appears to be the M1 subtype rather than the M3 subtype found in human and rat.     

Multipoint linkage analysis of the short arm of chromosome 11 in non-insulin dependent diabetes including maturity onset diabetes of youth

Summary Members of three families with maturity onset diabetes of youth (MODY) and seven with common type 2 diabetes were typed for six DNA markers (H-RAS, INS, HBBC, PTH, CALC1, CAT) on the short arm of chromosome 11. Using conventional pairwise linkage analysis, close linkage in the MODY families was excluded for all six markers. By multipoint analysis and a genetic map of the short arm of chromosome 11, MODY was excluded from a region of at least 35 and up to 60 centiMorgans (cM) on the short arm of chromosome 11. Multipoint analysis in the type 2 families also excludes linkage to the INS, H-RAS region of at least 3 and up to 30 cM. This study using multipoint linkage analysis in non-insulin dependent diabetes provides strong evidence against a role for mutations in or around the insulin gene in the causation of MODY or type 2 diabetes in the families studied.     

Transformation and regeneration of Brassica rapa using Agrobacterium tumefaciens

Summary Transformation and regeneration procedures for obtaining transgenic Brassica rapa ssp. oleifera plants are described. Regeneration frequencies were increasedby using silver nitrate and by adjusting the duration of exposure to 2,4-D. For transformation, Agrobacterium tumefaciens strain EHA101 containing a binary plasmid with the neomycin phosphotransferase gene (NPT II) and the b-glucuronidase gene (GUS) was cocultivated with hypocotyl explants from the oilseed B. rapa cvs. Tobin and Emma. Transformed plants were obtained within three months of cocultivation. Transformation frequencies for the cultivars Tobin and Emma were 1–9%. Evidence for transformation was shown by NPT II dot blot assay, the GUS fluorometric assay, Southern analysis, and segregation of the kanamycin-resistance trait in the progeny. The transformation and regeneration procedure described here has been used routinely to transform two cultivars of B. rapa and 18 cultivars of B. napus.     

Observation of inverted cubic phase in hydrated dioleoylphosphatidylethanolamine membranes

We report the observation of an inverted cubic phase in aqueous dispersions of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) by small-angle X-ray diffraction. DOPE is a paradigm in the study of nonlamellar phases in biological systems: it exhibits a well-known phase transition from the lamellar (L alpha) to the inverted hexagonal phase (HII) as the temperature is raised. The transition is observed to occur rapidly when a DOPE dispersion is heated from 2 degrees C, where the L alpha phase is stable, to 15 degrees C, where the HII phase is stable. We report on the induction of a crystallographically well-defined cubic lattice that is slowly formed when the lipid dispersion is rapidly cycled between -5 and 15 degrees C hundreds of times. Once formed, the cubic lattice is stable at 4 degrees C for several weeks and exhibits the same remarkable metastability that characterizes other cubic phases in lipid-water systems. X-ray diffraction indicates that the cubic lattice is most consistent with either the Pn3m or Pn3 space group. Tests of lipid purity after induction of the cubic indicate the lipid is at least 98% pure. The cubic lattice can be destroyed and the system reset by cycling the specimen several times between -30 and 2 degrees C. The kinetics of the formation of the cubic are dependent on the thermal history of the sample, overall water concentration, and the extreme temperatures of the cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Revised enzyme synthesis rate expression in cybernetic models of bacterial growth

A revised enzyme synthesis rate expression for cybernetic models of bacterial growth is presented. The rate expression, which is comprised of inducible and constitutive contributions, provides for a basal enzyme level that is necessary to predict certain types of commonly observed continuous culture transients. The response of a continuous culture to a step change in feed stream composition is simulated using both the old and new formulations, and the ramifications for the "matching-law" formulation are discussed.     

Three new species of Phacelia (Hydrophyllaceae) from Nuevo León,Mexico

Three new species ofPhacelia from Nuevo León, Mexico are described and illustrated. Two of these,P. hintoniorum andP. potosina, belong to theCrenulata group; the former, with included anthers, relates toP. coerulea; the latter, with exserted anthers, relates toP. alba orP. coulteri. The remaining novelty,P. zaragozana, belongs to the subgenusCosmanthus where its closest relationship is withP. laxa.     

Murine erythroleukemia cell variants: isolation of cells that have amplified the dihydrofolate reductase gene and retained the ability to be induced to differentiate

A series of murine erythroleukemia cell (MELC) variants was generated by selection for the ability to grow in increasing concentrations of the folate antagonist methotrexate (MTX). Growth of the parental MELC strain DS-19 was completely inhibited by 0.1 microM MTX. We isolated cells able to grow in 5, 40, 200, 400, and 800 microM MTX. Growth rates and yields were essentially the same in the presence or absence of the selective dose of MTX for all variants. MTX resistance was not the result of a transport defect. Dihydrofolate reductase (DHFR) from our variants and DS-19 was inhibited to the same extent by MTX. Variants had increased dihydrofolate reductase activities. The specific activity of DHFR was proportional to the selective concentration of MTX employed to isolate a given variant. DNA dot blotting established that the cloned variant (MR400-3) had a 160-fold increase in DHFR gene copy number relative to the parental strain (DS-19). Hybridization studies performed in situ established the presence of amplified DHFR genes on the chromosomes of the MTX-resistant but not the MTX-sensitive (parental) cells. Quantitation of DHFR mRNA by cytoplasmic dot blotting established that the amplified DHFR gene expression was proportional to gene copy number. Thus, MTX resistance was due to amplification of the DHFR gene. The variants retained the ability to be induced to differentiate in response to dimethyl sulfoxide and hexamethylenebis(acetamide) as evaluated by the criteria of globin mRNA accumulation, hemoglobin accumulation, cell volume decreases, and terminal cell division.(ABSTRACT TRUNCATED AT 250 WORDS)     

Polymer-supported RNA synthesis and its application to test the nearest-neighbor model for duplex stability

A solid-phase method using a phosphoramidite approach is described for synthesis of oligoribonucleotides. The method was used to synthesize pairs of oligomers with identical nearest neighbors but different sequences. Comparison of thermodynamic parameters for these pairs provides a test of the nearest-neighbor hypothesis for prediction of helix stability. In general, pairs of sequences with identical nearest neighbors have enthalpy and entropy changes for helix formation that differ by 8% on average, delta Go37 that differ by 6% on average, and melting temperatures within 0-5 degrees C of each other. These limits are typical of the accuracy that should be expected from nearest-neighbor predictions of RNA helix stability. UCAUGA and UGAUCA have the same nearest neighbors but melting temperatures that differ by 7 degrees C. This suggests some sequences will not be approximated well by the nearest-neighbor model.