Axon guidance: GTPases help axons reach their targets

During development and regeneration of the nervous system, axons must correctly navigate to their specific targets through a complex molecular environment. Recent work has shed light on how GTPases of the Ras family are involved in transducing extracellular signals into responses that lead to directed neurite outgrowth.     

Functional symmetry of UhpT, the sugar phosphate transporter of Escherichia coli

UhpT, the sugar phosphate transporter of Escherichia coli, acts to exchange internal inorganic phosphate for external hexose 6-phosphate. Because of this operational asymmetry, we studied variants in which right-side-out (RSO) or inside-out (ISO) orientations could be analyzed independently to ask whether the inward- and outward-facing UhpT surfaces have different substrate specificities. To study the RSO orientation, we constructed a histidine-tagged derivative, His10K291C/K294N, in which the sole external tryptic cleavage site (Lys294) had been removed. Functional assay as well as immunoblot analysis showed that trypsin treatment of proteoliposomes containing His10K291C/K294N led to loss of about 50% of the original population, reflecting retention of only the RSO population. To study the ISO orientation, we used a His10V284C derivative, in which a newly inserted external cysteine (Cys284) conferred sensitivity to the thiol-reactive agent, 3-(N-maleimidylpropionyl)biocytin. In this case, 3-(N-maleimidylpropionyl)biocytin treatment of proteoliposomes containing His10V284C gave about a 60% loss of activity, and immunodetection of biotin showed parallel modification of an equivalent fraction of the original population. Together, such findings indicate that the UhpT RSO and ISO orientations are in about equal proportion in proteoliposomes and that a single population can be generated by exposure of these derivatives to the appropriate agent. This allowed us to study proteoliposomes with UhpT functioning in RSO orientation (His10K291C/K294N) or ISO orientation (His10V284C) with respect to the kinetics of glucose 6-phosphate transport by phosphate-loaded proteoliposomes and also the inhibitions found with 2-deoxy-glucose 6-phosphate, mannose 6-phosphate, galactose 6-phosphate, fructose 6-phosphate, and inorganic phosphate. We found no significant differences in the behavior of UhpT in its different orientations, indicating that the transporter possesses an overall functional symmetry.     

The selective estrogen receptor modulator, raloxifene: a segment II/III delivery study in rats

Raloxifene is a nonsteroidal, selective estrogen receptor modulator developed by Eli Lilly and Company as a therapeutic agent for postmenopausal osteoporosis. Raloxifene was administered orally by gavage at doses of 0, 0.1, 1, or 10 mg/kg/d to female CD rats (25/group) on Gestation Day 6 (GD 6) through Postpartum Day 20 (PD 20). Females were allowed to deliver and maintain their progeny until PD 21. All dead pups and pups culled on PD 1 were given internal and external examinations. One pup/sex/litter was assigned to each of the following assessment groups: 1) the primary pair for the F1 generation study, in which survival, growth, development, behavior, indicators of sexual maturation, and reproductive performance were evaluated; 2) terminal necropsy evaluations at PD 21; 3) terminal necropsy evaluations at 60 d of age; and 4) assessments of immune function at 5 to 6 weeks of age. At termination on PD 21, 60, or approximately 140, a necropsy was performed; crown rump and tibia lengths were measured; pituitary weights were taken; and a portion of the anterior pituitary was retained for growth hormone, luteinizing hormone, and prolactin content determinations (control and 10-mg/kg groups only). The remainder of the pituitary and reproductive tissues were retained for histologic evaluations. Dose-related depressions in maternal body weight and food consumption occurred during gestation. Mean gestation length was increased at 1 and 10 mg/kg. Delayed, extended, and/or disrupted parturition occurred in dams given 10 mg/kg, which resulted in a high incidence of maternal morbidity and/or death, increased numbers of dead pups, and the survival of only 66% of live pups to PD 21. Progeny body weights were not decreased at birth, but were depressed progressively in a dose-related manner during the 3-week lactation period. Negative geotaxis and incisor eruption were apparently accelerated in the 1- and 10-mg/kg groups, but eye opening was delayed at 10 mg/kg. Postweaning activity levels, auditory startle, and passive avoidance performance were not affected in the raloxifene groups. Dose-related decreases in spleen cellularity and thymus weights occurred in both sexes, but immune system function, as measured by splenic natural killer cell activity and antibody response to sheep red blood cells, was not affected. Postweaning body weights and growth parameters, as well as pituitary hormone content, were affected in both an age- and sex-specific manner. Preputial separation was not affected, but vaginal patency occurred ca 2 d earlier than controls in females from the 10-mg/kg group. Estrous cycles of the F1 females were not affected during the first two weeks after vaginal opening, but were disrupted at 12 to 14 weeks of age in the 10-mg/kg group. These females showed poorer mating and fertility indices, and litter size was reduced in the two females that were pregnant. Histologically, reproductive organs were not affected in males at any age or in females at PD 21. At PD 60, vaginal mucification occurred in females from the 0.1- and 1-mg/kg groups. At PD 140, the only finding was a high rate of uterine hypoplasia in the 10-mg/kg group, and this finding occurred in the absence of any concomitant ovarian or vaginal changes. These reproductive and developmental findings are consistent with estrogen antagonist activity of raloxifene.     

The recognition of vowels produced by men, women, boys, and girls by cochlear implant patients using a six-channel CIS processor

Five patients who used a six-channel, continuous interleaved sampling (CIS) cochlear implant were presented vowels, in two experiments, from a large sample of men, women, boys, and girls for identification. At issue in the first experiment was whether vowels from one speaker group, i.e., men, were more identifiable than vowels from other speaker groups. At issue in the second experiment was the role of the fifth and sixth channels in the identification of vowels from the different speaker groups. It was found in experiment 1 that (i) the vowels produced by men were easier to identify than vowels produced by any of the other speaker groups, (ii) vowels from women and boys were more difficult to identify than vowels from men but less difficult than vowels from girls, and (iii) vowels from girls were more difficult to identify than vowels from all other groups. In experiment 2 removal of channels 5 and 6 from the processor impaired the identification of vowels produced by women, boys and girls but did not impair the identification of vowels produced by men. The results of experiment 1 demonstrate that scores on tests of vowels produced by men overestimate the ability of patients to recognize vowels in the broader context of multi-talker communication. The results of experiment 2 demonstrate that channels 5 and 6 become more important for vowel recognition as the second formants of the speakers increase in frequency.     

Clinical predictability of the waist-to-hip ratio in assessment of cardiovascular disease risk factors in overweight, premenopausal women

The waist-to-hip ratio (WHR) is one of the most commonly used anthropometric measures to indicate a central obesity pattern and an increased risk of cardiovascular disease in normal-weight women. Although the American Heart Association has reported that a WHR >0.80 be used to indicate increased risk of cardiovascular disease in women, the present study assessed the WHR above which is seen elevations in cardiovascular disease risk factors in a sample of overweight women. Using data from 240 women aged 27.5-47.5 y enrolled in a university weight-loss program, we determined WHR quartiles: <0.80, 0.80 to <0.84, 0.84 to <0.90, and > or =0.90. Subjects were placed into high-risk categories for cardiovascular disease on the basis of age- and population-defined norms. Women had an increased likelihood of elevated VLDL cholesterol, triacylglycerol, diastolic blood pressure, and composite risk (ie, having > or =4 cardiovascular disease risk factors) and an increased risk of having low concentrations of HDL at a WHR > or =0.90. All aforementioned variables had a significant odds ratio at a WHR > or =20.90 after adjustment for smoking, whereas elevated VLDL, triacylglycerol, and diastolic blood pressure were observed at this WHR after adjustment for a body mass index (in kg/m2) < or > or =35. Only 2 variables, VLDL and triacylglycerol, had a significant odds ratio at a WHR <0.90 before and after adjustment for BMI and smoking. These data suggest an upward shift in the critical threshold for WHR to > or =0.90, at which point there was an elevation in cardiovascular disease risk factors in already overweight women. This trend persisted regardless of whether the women smoked or whether their body mass index was < or > or =35.     

Field evaluation of the safety and efficacy of a temperature-sensitive Mycoplasma synoviae live vaccine

Mycoplasma synoviae (MS) strain MS-H was used in three separate commercial flocks for large-scale evaluation of the safety and efficacy of the vaccine under commercial conditions. MS-H successfully colonized meat and layer-breeders vaccinated by eyedrop and persisted for up to 55 wk after vaccination. Restriction fragment length polymorphism analysis showed that MS-H was the only strain isolated from two vaccinated flocks. In a third flock, challenge with a wild-type MS occurred, and this strain was isolated from both vaccinated and unvaccinated birds. Vertical transmission of MS-H was investigated by culturing pipped embryos and testing broiler progeny for MS antibody at processing (56 days old). No evidence of vertical transmission was detected. Lateral transmission of MS-H strain from vaccinated to unvaccinated birds occurred in one of the commercial flocks. Forty-one of 50 isolates of MS-H obtained from vaccinated flocks maintained their temperature-sensitive phenotype, but nine isolates showed a nontemperature-sensitive phenotype.     

Prophylactic effect of bovine anti-Cryptosporidium hyperimmune colostrum immunoglobulin in healthy volunteers challenged with Cryptosporidium parvum

Bovine hyperimmune anti-Cryptosporidium colostrum immunoglobulin (BACI) decreases the intensity of Cryptosporidium parvum infection in vitro. We investigated the prophylactic effect of BACI in healthy adults challenged with C. parvum. After we established an oocyst dose that resulted in 100% infection in four volunteers (baseline group), 16 volunteers were randomized to receive (1) BACI prior to C. parvum challenge (BACI group) and a nonfat milk placebo 30 minutes later, (2) BACI prior to and 30 minutes after challenge (reinforced BACI group), or (3) nonfat milk placebo prior to and 30 minutes after challenge. Subjects received BACI (10 g) or nonfat milk placebo three times a day for a total of 5 days and were followed for clinical symptoms and oocyst excretion for 30 days. A trend toward less diarrhea (P = .08) was observed for subjects receiving BACI in comparison with occurrences in placebo recipients. Subjects receiving BACI or nonfat milk placebo had a 100-fold reduction in oocyst excretion as compared with excretion in the baseline group.