Experimental Scrapie in the Mouse: Electrophoretic and Sedimentation Properties of the Partially Purified Agent

Abstract: High resolution purification procedures for the separation and characterization of neuropeptides are described. The methods, which are complementary, are based on ion exchange chromatography and reverse phase high pressure liquid chromatography and are designed to be used in conjunction with radioimmunoassays and bioassays for known peptides or structural identification in the case of peptides of unknown sequence. The high pressure liquid chromatographic method is versatile, highly reproducible and applicable to picomolar quantities of peptides and it gives very high resolution between most of the neuropeptides of present-day interest. The applicability of the method to the study of crude brain extracts is demonstrated.     

Dimethyl sulfoxide: reversible inhibitor of pollen tube growth

Five percent dimethyl sulfoxide (DMSO) completely inhibited tube initiation, stopped tube growth and suppressed the high respiration associated with tube growth of lily pollen. The effect of DMSO on respiration was indirect because uncoupling concentrations of 2,4-dinitrophenol abolished the inhibition of respiration. Five percent DMSO did not inhibit rapid starch synthesis during the first 30 minutes of incubation, nor did DMSO inhibit the period of high respiration associated with rapid starch synthesis. DMSO did not cause permanent damage to the cells since normal pollen tube growth occurred after its removal. Dimethyl sulfoxide is not a general inhibitor of pollen metabolism, but it may be a specific inhibitor of a process required for tube growth.     

An Infrared Spectrophotometric Study of Some Strains of Staphylococcus aureus

A method of obtaining expanded differential spectra of staphylococcal strains for comparative studies is described. Some differences found through the comparison of a large number of strains isolated from humans, turkeys, and other hosts are shown. No spectral characteristics that would associate a particular strain with its host were discerned. Differences in the strength of a band at 11.6 to 11.7 μ allowed division of the strains examined into two groups.     

Plasmodium falciparum: in vitro characterization and human infectivity of a cloned line.

The culture-adapted NF54 isolate of Plasmodium falciparum was subjected in vitro to three sequential limiting dilution titrations and the resulting clone was given the designation CVD1. DNA sequence analysis of the gene encoding the circumsporozoite (CS) protein revealed differences between CVD1 and the published NF54 CS gene. CVD1 had 1191 bp, 397 amino acids, and 42 repeat units while NF54 had 1218 bp, 405 amino acids, and 44 repeat units. The CVD1 clone was more sensitive to chloroquine than was the parental line, in vitro. Anopheles stephensi mosquitoes were infected equally by the cloned and uncloned parasites. Volunteers were readily infected by NF54 and CVD1 following infectious mosquito bites. The availability of a well-characterized, chloroquine-sensitive clone which safety infects humans should facilitate performance of experimental challenge studies to assess vaccine efficacy.     

Red Light-Regulated Growth : I. Changes in the Abundance of Indoleacetic Acid and a 22-Kilodalton Auxin-Binding Protein in the Maize Mesocotyl

We examined the changes in the levels of indoleacetic acid (IAA), IAA esters, and a 22-kilodalton subunit auxin-binding protein (ABP1) in apical mesocotyl tissue of maize (Zea mays L.) during continuous red light (R) irradiation. These changes were compared with the kinetics of R-induced growth inhibition in the same tissue. Upon the onset of continuous irradiation, growth decreased in a continuous manner following a brief lag period. The decrease in growth continued for 5 hours, then remained constant at 25% of the dark rate. The abundance of ABP1 and the level of free IAA both decreased in the mesocotyl. Only the kinetics of the decrease in IAA within the apical mesocotyl correlated with the initial change in growth, although growth continued to decrease even after IAA content reached its final level, 50% of the dark control. This decrease in IAA within the mesocotyl probably occurs primarily by a change in its transport within the shoot since auxin applied as a pulse moved basipetally in R-irradiated tissue at the same rate but with half the area as dark control tissue. In situ localization of auxin in etiolated maize shoots revealed that R-irradiated shoots contained less auxin in the epidermis than the dark controls. Irradiated mesocotyl grew 50% less than the dark controls even when incubated in an optimal level of auxin. However, irradiated and dark tissue contained essentially the same amount of radioactivity after incubation in [¹⁴C]IAA indicating that the light treatment does not affect the uptake into the tissue through the cut end, although it is possible that a small subset of cells within the mesocotyl is affected. These observations support the hypothesis that R causes a decrease in the level of auxin in epidermal cells of the mesocotyl, consequently constraining the growth of the entire mesocotyl.     

Cross sectional and longitudinal study of bone mineral content of the distal forearm in adult premenopausal women

The range of fat corrected distal forearm mineral content (FMC) (at a site which comprises approximately 75% cortical and 25% trabecular bone) and the effect of aging on FMC were determined in normal premenopausal women. In 106 women (mean age 39; range 18-56) the mean FMC was 1.184 (SD 148) g/cm; fat correction increased this to 1.239 (SD 148) g/cm. There were significant correlations between fat corrected FMC and height, weight and BMI (r greater than 0.16; P less than 0.05). In 43 of these women (mean age 35; range 18-51) repeat measurements of FMC were performed. The last measurement was separated from the first by a mean time interval of 27 +/- 3 months. There was no significant change in uncorrected FMC (baseline 1.185 +/- 0.21 g/cm compared with their final measurement 1.182 +/- .020 g/cm; P = 0.51). Fat-corrected FMC (baseline 1.229 +/- .021 g/cm compared with 1.223 +/- .020 g/cm later) tended to decrease although this change was not significant (P = 0.06). Age ranked cusum analysis demonstrated a non-significant fat-corrected rate of change in FMC of -.3% yr in those over 35 years of age (P less than 0.10). This data suggests that if there is any distal forearm bone loss before the menopause it is negligible.     

Identification of active site residues of Escherichia coli fumarate reductase by site-directed mutagenesis.

Menaquinol-fumarate oxidoreductase of Escherichia coli is a four-subunit membrane-bound complex that catalyzes the final step in anaerobic respiration when fumarate is the terminal electron acceptor. The enzyme is structurally and catalytically similar to succinate dehydrogenase (succinate-ubiquinone oxidoreductase) from both procaryotes and eucaryotes. Both enzymes have been proposed to contain an essential cysteine residue at the active site based on studies with thiol-specific reagents. Chemical modification studies have also suggested roles for essential histidine and arginine residues in catalysis by succinate dehydrogenase. In the present study, a combination of site-directed mutagenesis and chemical modification techniques have been used to investigate the role(s) of the conserved histidine 232, cysteine 247, and arginine 248 residues of the flavorprotein subunit (FrdA) in active site function. A role for His-232 and Arg-248 of FrdA is shown by loss of both fumarate reductase and succino-oxidase activities following site-directed substitution of these particular amino acids. Evidence is also presented that suggests a second arginine residue may form part of the active site. Potential catalytic and substrate-binding roles for arginine are discussed. The effects of removing histidine-232 of FrdA are consistent with its proposed role as a general acid-base catalyst. The fact that succinate oxidation but not fumarate reduction was completely lost, however, might suggest that alternate proton donors substitute for His-232. The data confirm that cysteine 247 of FrdA is responsible for the N-ethylmaleimide sensitivity shown by fumarate reductase but is not required for catalytic activity or the tight-binding of oxalacetate, as previously thought.     

Disclosure of sexual preference to physicians by black lesbian and bisexual women.

Physicians'' ability to diagnose and treat health care problems, particularly those with a psychosocial component, is facilitated by accurate information concerning the life-styles of their patients. White lesbians have been shown to be generally reluctant to disclose sexual orientation to their physicians, but little, if anything, is known about black lesbians. Black women, self-identified as bisexuals (N = 65) and lesbians (N = 529), were asked whether they had disclosed their homosexual behavior to their physicians. In the sample, only a third of the women had. Previous sexual experiences, both heterosexual and homosexual, were also queried to illuminate patterns of gynecologic health risk factors. Nearly all of the women reported previous heterosexual experiences.     

Comparisons of ruminal fermentation characteristics and microbial populations in bison and cattle

Ruminal microbial populations, fermentation characteristics, digestibility, and liquid flow rates in two ruminally cannulated bison and two ruminally cannulated Hereford steers fed a prairie hay diet were compared. No significant differences in anaerobic bacterial counts, volatile fatty acid concentrations, or ruminal pHs were evident between bison and cattle. Also, no significant differences in neutral detergent fiber digestibility, indigestible fiber retention time, or intake were detected between bison and cattle, although cattle had higher levels (P less than 0.08) of ruminal dry matter and indigestible fiber than bison. Bison had a smaller (P = .02) ruminoreticular volume, faster liquid dilution rates, and faster liquid turnover times than cattle. The average ruminal ammonia nitrogen concentration was higher (P = 0.02) in bison (1.17 mg/dl) than in cattle (0.79 mg/dl). Total ciliate protozoal counts and cell volume were greater (P = 0.07) in bison (32.8 x 10(4)/g and 407.1 x 10(-4) ml/g, respectively) than in cattle (15.7 x 10(4)/g and 162.2 x 10(-4) ml/g, respectively). Bison harbored higher (P less than 0.02) numbers of Dasytricha spp., Eudiplodinium maggii, Eudiplodinium bursa, and Epidinium spp. than cattle and possessed a type B protozoan population. The cattle possessed a mixed type A-type B population that was characterized by Ophryoscolex spp. and Polyplastron spp. in association with low concentrations of Epidinium spp. and Eudiplodinium maggii.     

Monitoring for insecticide resistance in field-collected strains of the German cockroach (Dictyoptera: Blattellidae)

Forty-five field-collected strains of German cockroaches, Blattella germanica were tested for resistance to 12 different insecticides by the time-mortality response method in comparison with a known susceptible strain. Only low to moderate resistance to diazinon, chlorpyrifos, and acephate was detected. Resistance to malathion was widespread; about half of the strains tested showed high resistance. High resistance to the carbamates propoxur and bendiocarb also occurred. High resistance was uncommon with propoxur, but about 35 strains were highly resistant to bendiocarb. High resistance to pyrethrins was observed in about of the strains tested. Resistance to the pyrethroids allethrin, permethrin, phenothrin, fenvalerate, and cyfluthrin was detected in some of the strains examined. All of the strains tested were susceptible to one or more of the insecticides used. These results indicate that, although resistance is a serious problem in this species, satisfactory control should be possible by selection of an appropriate insecticide.