Ion-Exchange Chromatography Separates Activities Synthesizing and Degrading Fructose 2,6-Bisphosphate from C3 and C4 Leaves but Not from Rat Liver

Fructose-6-phosphate,2-kinase and fructose-2,6-bisphosphatase were separated on the basis of charge from leaves of C₃ (spinach, lettuce, and pea) and C₄ (sorghum and amaranthus) plants but not from rat liver—a tissue known to contain a bifunctional enzyme with both activities. [2-³²P]Fructose 2,6-bisphosphate binding experiments also suggest that the major forms of these activities reside on different proteins in leaves.     

The economics of clinical genetics services. III. Cognitive genetics services are not self-supporting.

We investigated the amount of time required to provide, and the charges and reimbursement for, cognitive genetics services in four clinical settings. In a prenatal diagnostic center, a mean of 3 h/couple was required to provide counseling and follow-up services with a mean charge of $30/h and collection of $27/h. Only 49% of personnel costs were covered by income from patient charges. In a genetics clinic in a private specialty hospital, 5.5 and 2.75 h were required to provide cognitive services to each new and follow-up family, respectively. The mean charge for each new family was $25/h and for follow-up families $13/h. The amount collected was less than 25% of that charged. In a pediatric genetics clinic in a large teaching hospital, new families required a mean of 4 h and were charged $28/h; follow-up families also required a mean of 4 h, and were charged $15/h. Only 55% of the amounts charged were collected. Income from patient charges covered only 69% of personnel costs. In a genetics outreach setting, 5 and 4.5 h were required to serve new and follow-up families, respectively. Charges were $25/h and $12/h, and no monies were collected. In all clinic settings, less than one-half of the total service time was that of a physician, and more than one-half of the service time occurred before and after the clinic visit. In no clinic setting were cognitive genetics services self-supporting. Means to improve the financial base of cognitive genetics services include improving collections, increasing charges, developing fee schedules, providing services more efficiently, and seeking state, federal, and foundation support for services.     

Anthecology ofSchrankia nuttallii (Mimosaceae) on the tallgrass prairie

Schrankia nuttalii flowers through late spring on the tallgrass prairie. Although each stem produces an average of 26 capitate inflorescences only 12% of those inflorescences will open each day to disperse and receive polyads. Each inflorescence may live up to 48 hours but anthers abscise by late afternoon on the first day and the filaments change color and lose their scent. The 78–93 florets comprising each inflorescence open synchronously before dawn or during early morning hours. First day inflorescences ofS. nuttallii are herkogamous and fragrant. They are nectarless. Bombyliid flies and male bees are infrequent floral foragers so the major pollinators include female bees representing five families;Anthophoridae, Apidae, Colletidae, Halictidae, andMegachilidae. All foraging insects ignore second day inflorescences although stigmas are still receptive. Although 97% of all bees collected onS. nuttallii carrySchrankia polyads in their scopae or corbiculae 59% also carry the pollen/pollinaria of one or more coblooming angiosperms. At least 98% of all bees carrying mixed pollen loads incorporate the pollen/pollinaria of one or more nectariferous taxa (e.g.Asclepias spp.,Asteraceae, Convolvulaceae, Delphinium spec., etc.). Species of halictid bees are more likely to carry pure loads ofS. nuttallii polyads (70%) than bees of the four remaining families. Due to the nectarless florets and high degree of polylectic foraging bee-pollination inS. nuttallii converges more closely with the pollination systems of some AustralianAcacia spp. than with most other xeric/tropical genera of mimosoids studied in the western hemisphere.     

Pressure-Induced Alterations in the Protein Pattern of the Thermophilic Archaebacterium Methanococcus thermolithotrophicus

Elevated hydrostatic pressure has been shown to affect the growth rate of the thermophilic methanobacterium Methanococcus thermolithotrophicus without extending its temperature range of viability. Analysis of the cell inventory after ≈ 10 h of incubation at 65°C and 50 MPa (applying high-pressure liquid chromatography and two-dimensional gel electrophoresis) proved that pressure induces alterations in the protein pattern and the amino acid composition of the total cell hydrolysate. Gels showed that after pressurization a series of (basic) proteins with a molecular mass in the range of 38 and 70 kilodaltons occurs which is not detectable in cells grown at normal atmospheric pressure. The question of whether the observed alterations are caused by the perturbation of the balance of protein synthesis and turnover or by the pressure-induced synthesis of compounds analogous to heat shock proteins remains unanswered.     

Applications of fluorochromes to pollen biology. II. The DNA probes ethidium bromide and Hoechst 33258 in conjunction with the callose-specific aniline blue fluorochrome

Techniques are described for detection of pollen grain and pollen tube nuclei using the fluorescent DNA probes ethidium bromide or Hoechst 33258, in conjunction with the aniline blue fluorochrome sirofluor, which stains the callose component of pollen tube walls and plugs. The DNA probes, which may be used either as vital stains or following fixation, permit discrimination between vegetative and generative or sperm nuclei. Double staining with sirofluor allows location of nuclei within pollen tubes grown in vitro, and when used after pollination enables the viewer to discriminate between nuclei within the pollen tube vs. nuclei of the pistil tissue.     

Scleroblast cultures from the gorgonianLeptogorgia virgulata (Lamarck) (Coelenterata: Gorgonacea)

Summary Scleroblasts were separated from fragmented tissue of growing tips ofLeptogorgia virgulata and cultured using a modification of the technique of Rannou. Replacement of fetal bovine serum with horse serum seemed to increase scleroblast viability. Cell adhesion occurred from 14 to 43 d. Cultured scleroblasts demonstrated cell aggregation, spicule formation, and extrusion of spicules into the external medium. Cells showing spicules in the process of being extruded appeared on the average after 24 d of culture. Variability among cultures was marked with respect to both division and spicule formation. Healthy cultures were maintained for more than 4 mo. This work was supported by National Science Foundation grants PCM8201389 and DCB8502698. This is contribution No. 674 of Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina.     

Fluorescent energy transfer measurements on fluorescein isothiocyanate modified cytochrome P-450 LM2

The distance between the heme iron and the N-terminus of cytochrome P-450 LM2 was determined by fluorescence energy transfer measurements. Fluorescein isothiocyanate which was covalently bound to the N-terminal methionine was used as donor chromophor. The Ro value between fluorescein isothiocyanate and the heme was calculated to be 3.98 nm. The distance between the nitrogen of the N-terminal methionine and the heme was estimated with 2.84 +/- 0.23 nm excluding most likely the N-terminal amino acid of cytochrome P-450 LM2 to participate in the electron transfer to the heme iron. A cytochrome P-450 LM2 membrane model is proposed.     

Role of aminocyclopropane-l-carboxylic acid in ethylene release by distal tissues following localized application of ethephon in Cucurbita pepo

The application of ethephon to a single leaf of Cucurbita pepo L. cv. Trailing Marrow plants caused a huge increase in ethylene production from the treated organ and an increased rate of ethylene production from other parts of the plant. These increases were particularly marked in the shoot apex and expanding leaf. Prior treatment with aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor, blocked the increased production of ethylene at sites distant from the point of ethephon application. This strongly suggests that the increased ethylene production at these distant sites is due to ethylene biosynthesis and not a result of the translocation of ethylene released by the breakdown of ethephon at the site of application. Assays of 1-aminocyclopropane-l-carboxylic acid (ACC), an ethylene precursor, showed that it increased substantially after ethephon application but was at undetectable levels in the presence of AVG. It is proposed that the application of ethephon stimulates ethylene biosynthesis, but that transport through the plants is effected by ACC which is then converted to ethylene at the shoot apex and leaves.