The Ypt1 GTPase is essential for the first two steps of the yeast secretory pathway.

Small GTPases of the rab family are involved in the regulation of vesicular transport. The restricted distribution of each of these proteins in mammalian cells has led to the suggestion that different rab proteins act at different steps of transport (Pryer, N. K., L. J. Wuestehube, and R. Sheckman. 1992. Annu Rev. Biochem. 61:471-516; Zerial, M., and H. Stenmark. 1993. Curr. Opin. Cell Biol. 5:613-620). However, in this report we show that the Ypt1-GTPase, a member of the rab family, is essential for more than one step of the yeast secretory pathway. We determined the secretory defect conferred by a novel ypt1 mutation by comparing the processing of several transported glycoproteins in wild-type and mutant cells. The ypt1-A136D mutant has a change in an amino acid that is conserved among rab GTPases. This mutation leads to a rapid and tight secretory block upon a shift to the restrictive temperature, and allows for the identification of the specific steps in the secretory pathway that directly require Ypt1 protein (Ypt1p). The ypt1-A136D mutant exhibits tight blocks in two secretory steps, ER to cis-Golgi and cis- to medial-Golgi, but later steps are unaffected. Thus, it is unlikely that Ypt1p functions as the sole determinant of fusion specificity. Our results are more consistent with a role for Ypt1/rab proteins in determining the directionality or fidelity of protein sorting.

Requirement of nucleotide exchange factor for Ypt1 GTPase mediated protein transport.

Small GTPases of the rab family are involved in the regulation of vesicular transport. It is believed that cycling between the GTP- and GDP-bound forms, and accessory factors regulating this cycling are crucial for rab function. However, an essential role for rab nucleotide exchange factors has not yet been demonstrated. In this report we show the requirement of nucleotide exchange factor activity for Ypt1 GTPase mediated protein transport. The Ypt1 protein, a member of the rab family, plays a role in targeting vesicles to the acceptor compartment and is essential for the first two steps of the yeast secretory pathway. We use two YPT1 dominant mutations that contain alterations in a highly conserved GTP-binding domain, N121I and D124N. YPT1-D124N is a novel mutation that encodes a protein with nucleotide specificity modified from guanine to xanthine. This provides a tool for the study of an individual rab GTPase in crude extracts: a xanthosine triphosphate (XTP)-dependent conditional dominant mutation. Both mutations confer growth inhibition and a block in protein secretion when expressed in vivo. The purified mutant proteins do not bind either GDP or GTP. Moreover, they completely inhibit the ability of the exchange factor to stimulate nucleotide exchange for wild type Ypt1 protein, and are potent inhibitors of ER to Golgi transport in vitro at the vesicle targeting step. The inhibitory effects of the Ypt1-D124N mutant protein on both nucleotide exchange activity and protein transport in vitro can be relieved by XTP, indicating that it is the nucleotide-free form of the mutant protein that is inhibitory. These results suggest that the dominant mutant proteins inhibit protein transport by sequestering the exchange factor from the wild type Ypt1 protein, and that this factor has an essential role in vesicular transport.

GTP hydrolysis is not important for Ypt1 GTPase function in vesicular transport.

GTPases of the Ypt/Rab family play a key role in the regulation of vesicular transport. Their ability to cycle between the GTP- and the GDP-bound forms is thought to be crucial for their function. Conversion from the GTP- to the GDP-bound form is achieved by a weak endogenous GTPase activity, which can be stimulated by a GTPase-activating protein (GAP). Current models suggest that GTP hydrolysis and GAP activity are essential for vesicle fusion with the acceptor compartment or for timing membrane fusion. To test this idea, we inactivated the GTPase activity of Ypt1p by using the Q67L mutation, which targets a conserved residue that helps catalyze GTP hydrolysis in Ras. We demonstrate that the mutant Ypt1-Q67L protein is severely impaired in its ability to hydrolyze GTP both in the absence and in the presence of GAP and consequently is restricted mostly to the GTP-bound form. Surprisingly, a strain with ypt1-Q67L as the only YPT1 gene in the cell has no observable growth phenotypes at temperatures ranging from 14 to 37 degrees C. In addition, these mutant cells exhibit normal rates of secretion and normal membrane morphology as determined by electron microscopy. Furthermore, the ypt1-Q67L allele does not exhibit dominant phenotypes in cell growth and secretion when overexpressed. Together, these results lead us to suggest that, contrary to current models for Ypt/Rab function, GTP hydrolysis is not essential either for Ypt1p-mediated vesicular transport or as a timer to turn off Ypt1p-mediated membrane fusion but only for recycling of Ypt1p between compartments. Finally, the ypt1-Q67L allele, like the wild type, is inhibited by dominant nucleotide-free YPT1 mutations. Such mutations are thought to exert their dominant phenotype by sequestration of the guanine nucleotide exchange factor (GNEF). These results suggest that the function of Ypt1p in vesicular transport requires not only the GTP-bound form of the protein but also the interaction of Ypt1p with its GNEF.

Identification of regulators for Ypt1 GTPase nucleotide cycling.

Small GTPases of the Ypt/Rab family are involved in the regulation of vesicular transport. Cycling between the GDP- and GTP-bound forms and the accessory proteins that regulate this cycling are thought to be crucial for Ypt/Rab function. Guanine nucleotide exchange factors (GEFs) stimulate both GDP loss and GTP uptake, and GTPase-activating proteins (GAPs) stimulate GTP hydrolysis. Little is known about GEFs and GAPs for Ypt/Rab proteins. In this article we report the identification and initial characterization of two factors that regulate nucleotide cycling by Ypt1p, which is essential for the first two steps of the yeast secretory pathway. The Ypt1p-GEF stimulates GDP release and GTP uptake at least 10-fold and is specific for Ypt1p. Partially purified Ypt1p-GEF can rescue the inhibition caused by the dominant-negative Ypt1p-D124N mutant of in vitro endoplasmic reticulum-to-Golgi transport. This mutant probably blocks transport by inhibiting the GEF, suggesting that we have identified the physiological GEF for Ypt1p. The Ypt1p-GAP stimulates GTP hydrolysis by Ypt1p up to 54-fold, has a higher affinity for the GTP-bound form of Ypt1p than for the GDP-bound form, and is specific to a subgroup of exocytic Ypt proteins. The Ypt1p-GAP activity is not affected by deletion of two genes that encode known Ypt GAPs, GYP7 and GYP1, nor is it influenced by mutations in SEC18, SEC17, or SEC22, genes whose products are involved in vesicle fusion. The GEF and GAP activities for Ypt1p localize to particulate cellular fractions. However, contrary to the predictions of current models, the GEF activity localizes to the fraction that functions as the acceptor in an endoplasmic reticulum-to-Golgi transport assay, whereas the GAP activity cofractionates with markers for the donor. On the basis of our current and previous results, we propose a new model for the role of Ypt/Rab nucleotide cycling and the factors that regulate this process.

Acupressure for nausea and vomiting of pregnancy: a randomized, blinded study.

OBJECTIVE: To evaluate the effectiveness of acupressure in reducing nausea and vomiting of pregnancy. METHODS: Symptomatic pregnant women were randomized to one of two acupressure groups: one treatment group using an acupressure point (PC-6) and one sham control group using a placebo point. Subjects were blind to the group assignment. Each evening for 10 consecutive days, the subjects completed an assessment scale describing the severity and frequency of symptoms that occurred. Data from the first 3 days were used as pre-treatment scores. Beginning on the morning of the fourth day, each subject used acupressure at her assigned point for 10 minutes four times a day. Data from day 4 were discarded to allow 24 hours for the treatment to take effect. Data from days 5-7 were used to measure treatment effect. RESULTS: Sixty women completed the study. There were no differences between groups in attrition, parity, fetal number, maternal age, gestational age at entry, or pre-treatment nausea and emesis scores. Analysis of variance indicated that both groups improved significantly over time, but that nausea improved significantly more in the treatment group than in the sham control group (F1,58 = 10.4, P = .0021). There were no differences in the severity or frequency of emesis between the groups. There was a significant positive correlation (r = 0.261, P = .044) between maternal age and severity of nausea. CONCLUSIONS: Our results indicate that acupressure at the PC-6 anatomical site is effective in reducing symptoms of nausea but not frequency of vomiting in pregnant women.

Single photon emission computed tomographic evaluation of brainstem release phenomenon and seizure in neonates.

We report the ictal brain single photon emission computed tomographic (SPECT) findings in two neonates. One neonate had hypoxic-ischemic encephalopathy, a disorganized discontinuous electroencephalogram (EEG) background, lethargy, seizures, and brainstem release phenomena. A brain SPECT was performed during a brainstem release phenomenon characterized by a 34-second sustained tonic posture of the right arm and chewing. It did not reveal focal cerebral hemisphere hyperfusion. The second neonate had hemimegalencephaly, low-voltage irregular EEG background, and seizures. A brain SPECT was performed during a seizure characterized by a 32-second sustained tonic posture of the right arm. It revealed focal hyperperfusion in the posterior region of the left hemisphere. The brain SPECT findings in these patients indicate that despite clinically similar events, brainstem release phenomena and seizures have different perfusion characteristics, and refute the theory that brainstem release phenomena are due to epileptic foci in the cerebral hemispheres undetectable by EEG.

Similar brain SPECT findings in subclinical and clinical seizures in two neonates with hemimegalencephaly.

Brain single-photon emission computed tomography (SPECT) findings during clinical and subclinical seizures were compared in two neonates with hemimegalencephaly. Interictal and ictal brain SPECT were performed in two neonates. The ictal studies were performed during a clinical seizure in one neonate and during a subclinical seizure in another neonate. They revealed similar focal hemispheric hyperperfusion at the electroencephalographic seizure foci in both cases. The similar perfusion patterns imply that clinical and subclinical seizures place similar metabolic demands on the cerebral tissue involved in the generation of electroencephalographic seizures in neonates with cerebral dysgenesis and suggest that clinical and subclinical seizures should be treated similarly in this population.

The effect of mode of delivery on long-term outcome of very low birthweight infants.

A prospective 2-year neurodevelopmental follow-up was carried out on 69 very low birthweight (VLBW) infants (< 1501 g), born in the years 1985-87. The aim of the study was to determine whether there was a long-term advantage to cesarean section in these infants. The incidence of major disability and cognitive ability at 2 years of age were assessed, comparing modes of delivery. Cesarean section was performed in 38 out of 69 (55.1%) of the infants. Major disability was diagnosed in 11/69 (15.9%) of the children, of whom 7/38 (18.4%) were delivered by cesarean section, compared with 4/31 (12.9%) delivered vaginally. The difference, accounting for presentation and multiple birth was not statistically significant. Cognitive ability at 2 years of age was tested using the Mental Development Index (MDI) of the Bayley Scales, and was compared, according to mode of delivery, in 55 of 58 infants without major disability. There was no statistically significant difference between mean +/- S.E. in the MDI of 28 infants delivered by cesarean section (99.7 +/- 7.3) and that of 27 infants delivered vaginally (95.6 +/- 4). In summary, at 2 years of age, no clinically relevant benefit was found for VLBW infants who had been delivered by cesarean section.

The familial ovarian cancer registry: progress report.

BACKGROUND: Ovarian cancer can be cured if detected early enough, but usually has already metastasized when diagnosed. A family history of ovarian cancer is still the strongest known risk factor. OBJECTIVE: To identify women at risk for ovarian cancer and design a program of surveillance. METHODS: Prospective registry of women with a family history of ovarian cancer. RESULT: From April 1991 to July 1993, 137 women (119 families), mean age 43, registered with the Familial Ovarian Cancer Registry. The 119 pedigrees revealed 171 cases of ovarian cancer. Only one family is undocumented by pathology. Forty of 137 registrants have more than one relative with ovarian cancer. Six percent of pelvic examinations were abnormal for potential adnexal disease. In 4% of registrants, initial CA125 concentrations were abnormal. Ultrasound examinations were abnormal in ovarian size (5%), in morphology (3%), and by resistive indices (4%). Four ultrasounds were repeated earlier than routine. Using "standard" fees, the total cost to diagnose the one case of ovarian cancer discovered was $68,848. CONCLUSIONS: This approach still cannot be considered cost-effective. We are continuing to search for genetic and molecular markers of disease in women at greatest risk and in their affected relatives.

Evaluation of the approach of primary care physicians to the management of streptococcal pharyngotonsillitis. IPROS Network.

BACKGROUND: Streptococcal pharyngotonsillitis remains a common illness in children and can lead to serious complications if left untreated. OBJECTIVE: To evaluate the diagnostic and management approach of a sample of primary care physicians in the largest sick fund in Israel to streptococcal pharyngotonsillitis in children. METHODS: A questionnaire was mailed to all physicians who treat children and are employed by the General Health Services (Kupat Holim Klalit) in the Jerusalem District. The questionnaire included data on demographics, practice type and size, and availability of throat culture and rapid strep test; as well as a description of three hypothetical cases followed by questions relating to their diagnosis and treatment. RESULTS: Of the 188 eligible physicians, 118 (62.5%) responded, including 65 of 89 pediatricians (73%) and 53 of 99 family and general practitioners (53.5%). Fifty-six physicians (47.4%) had more than 18 years experience, and 82 (70%) completed specialization in Israel. Mean practice size was 950 patients. Fifty-three physicians (43%) worked in Kupat Holim community clinics, 25 (21%) worked independently in private clinics, and 40 (34%) did both. A total of 91 (77%) had access to laboratory facilities for daily throat culture. The time it took for the results to arrive was 48 to 72 hours. For the three clinical scenarios, 90% of the physicians accurately evaluated case A, a 1-year-old with viral pharyngotonsillitis, and 100 (85%) correctly diagnosed case C, a 7-year-old with streptococcal infection. As expected, opinions were divided on case B, a 3-year-old child with uncertain diagnosis. Accordingly, 75 (65.3%) physicians did not recommend treatment for case A, compared to 109 (92.5%) for case C. For case B, 22 (19%) said they would always treat, 43 (36%) would sometimes treat, and 35 (30%) would await the result of the throat culture. For 104 (88%) physicians the antibiotic of choice for case C was penicillin, while only 9 (7.5%) chose amoxicillin. However, the recommended dosage regimens varied from 250 to 500 mg per dose, and from two to four doses daily. For case C, 110 physicians (93%) chose a 10 day duration of treatment. CONCLUSIONS: The primary care physicians in the sample (pediatricians, general practitioners and family physicians) accurately diagnosed viral and streptococcal pharyngotonsillitis. However, there was a lack of uniformity regarding its management in general, and the dosage regimen for penicillin in particular.

Class II, division 2 malocclusion. To extract--or not extract?

Identical 13-year-old twin boys with Class II, division 2 malocclusions are treated at the same time, one with a full complement of teeth and the other with extraction of the first bicuspids.

[Screening for congenital hip dislocation in Belgium. Results of a survey in maternity wards. Proposals]. / Le dépistage de la maladie luxante de la hanche en Belgique. Résultats de l'enquête dans les maternités. Propositions.

Congenital dislocation of the hip (CDH) is probably more frequent in our country than generally appreciated. In most European countries, the incidence of CDH varies from 6 to 20 per thousand living births. The screening for the condition is organized with the help of public services. Our purpose was to survey the maternity wards to estimate the extent of the occurrence in Belgium. A volunteer orthopedic surgeon met with the pediatrician and the obstetrician in every hospital with a maternity ward to complete a questionnaire. We present a detailed analysis of the results of the survey and propose a better system for screening.

[What becomes of the interposed capsule in Colonna's arthroplasty?]. / Que devient la capsule interposée dans l'arthroplasie de Colonna?

A total hip replacement had to be performed 25 years after a Colonna arthroplasty. The acetabulum has been cut off for examination (articular cartilage and subchondral bone). The evolution of the case is detailed. Histological examination shows that the capsular tissue became articular cartilage, but not a normal one. This observation confirms that Colonna arthroplasty can give a good joint for more than 20 years but not longer.

[Coxa vara. Isolated growth of the greater trochanter. Prevention-treatment]. / Coxa vara. Croissance isolée du grand trochanter. Prévention-traitement.

Prevention of avascular complications is a primary aim. The ischemic insult to the femoral head provokes different types of morphologic deformities depending on its location. When the lateral part of the growth plate is affected, the head will be in valgus with a short neck, on the contrary, when the medial part is affected, a coxa vara occurs. The sooner the growth is stopped, the shorter the neck will be. Nevertheless, the greater trochanter will continue its growth and under certain conditions, will extend beyond the head. The Articulo-Trochanteric Distance is a measurement of the deformity which may be checked regularly. Early recognition permits prevention and adequate treatment. Treatment options include epiphysiodesis of the greater trochanter before the age of 8 to 10 years, trochanteric repositioning with osteotomy, and valgus osteotomy (Pauwels' Y-osteotomy).

[Comparative study of a series of normal knees and a series of knees with patellar instability]. / Etude comparative d'une série de genoux normaux et d'une série de genoux à rotule instable.

In studying the long-term follow-up of 39 cases of patellofemoral instability operated in our department for recurrent dislocation, we also analyzed their morphological appearance on X-ray. We compared the data given by Maldague and Malghem, Dejour and Walch for the pathological conditions of our cases with the same number of normal knees. This comparative analysis showed that measuring the bulging of the upper part of the trochlea and the depth of its groove on a lateral view is a reliable method to evaluate patellar instability. The classical axial view gives less useful information to quantify the instability. However, this axial view shows a particular aspect in the cases of severe instability: the fulcrum of the trochlea is displaced inwards while the inner trochlear facet is smaller or even absent. This precise radiological examination and the complete clinical examination with an analysis of the "morphotype" (Lerat) are necessary in the screening, diagnosis and treatment of severe patellofemoral instability.

[Treatment of major patellar instability. Results of the Fèvre-Dupuis operation]. / Traitement de l'instabilité rotulienne majeure. Résultat de l'opération de Fèvre-Dupuis.

In the treatment of recurrent subluxation and dislocation of the patella in adolescents and young adults, the authors describe a method consisting of: --a modified Roux procedure for internal transposition and advancement of the anterior tibial tuberosity; --the Lecène technic for over-the-top reinsertion of the vastus medialis on the lateral aspect of the patella. All the patients had a plaster cast for 10 days followed by rehabilitation until normal knee function was achieved. Stiff knees were mobilized under general anesthesia. Normal activity was progressively resumed 6 weeks after surgery. Out of the 31 patients (41 knees) available for objective follow-up evaluation, 26 were women and 5 men, with an average age of 19 years. The mean follow-up period was 9 and a half years with a minimum of 2 years and a maximum of 23. End results in terms of relief of pain, patellar stability and knee function were gratifying. Thirty knees were rated good, 8 fair and 3 poor. No recurrence of subluxation or dislocation was found.

[Pathology of the anterior peroneus tendon and that of the intermetatarsal bone]. / La pathologie du tendon du péronier antérieur et celle de l'os intermétatarsien.

The inconstant peroneus tertius is the fourth muscle in the antero-lateral aspect of the leg. Its tendon crosses the fourth tendon of the extensor hallucis brevis on the dorsal aspect of the cuboïdo-metatarsal joint. If an impingement occurs it may provoke a painful condition and a typical synovial cyst. The anatomy and the pathology of the condition are described. The treatment is very simple: the inconstant tendon should be removed when it produces symptoms. An accessory bone, the intermetatarsal bone, located at the proximal part of the first intermetatarsal or intercuneiform space, may have various shapes. It can provoke pain in the first space when pressure is exerted on capsulo-ligamentous structures or on neuro-vascular elements. The treatment is excision of the accessory bone.

[Hemi-arthroplasty of the shoulder: radiological, functional and dynamic studies]. / L'hémi-arthroplastie d'épaule: étude radiologique, fonctionnelle et dynamique.

From September 1973 to October 1992, forty-three shoulder arthroplasties were performed in forty-one patients with complicated fractures or degenerative disease. Radiological and functional assessment with a mean follow-up time of forty-five months permitted us to review twenty patients with fifteen Neer II prosthesis, three isoelastic prosthesis and two total shoulder replacements. Of these, eleven presented with traumatic injuries and four with degenerative disease. The mean age at operative time was 61 years. Radiological evaluation showed that all cases had a retroversion of about 30 degrees. Normal humeral length and lateral shifting were not achieved in most patients; in fact only one had a restored length and lateral shifting. The mean scapulothoracic range of motion was found to be half that of a normal gliding shoulder (angle 30 degrees instead of 60 degrees). The subacromial space was diminished by one third in all cases. Relief of shoulder pain was the most significant finding. Mobility was restored to a level of about 75% of normal according to Constant's Scale. Dynamometric measures showed an important loss of force (47% of normal) despite a normal external rotation force. Recent improvements in implant conception (modular prosthesis) and a better understanding of physiological shoulder mechanisms should improve the functional results of this arthroplasty in the future.