How potassium affects the activity of the molecular chaperone Hsc70. I. Potassium is required for optimal ATPase activity

Several functions of the 70-kilodalton heat shock cognate protein (Hsc70), such as peptide binding/release and clathrin uncoating, have been shown to require potassium ions. We have examined the effect of monovalent ions on the ATPase activity of Hsc70. The steady-state ATPase activities of Hsc70 and its amino-terminal 44-kDa ATPase fragment are minimal in the absence of K+ and reach a maximum at approximately 0.1 M [K+]. Activation of the ATPase turnover correlates with the ionic radii of monovalent ions; those that are at least 0.3 A smaller (Na+ and Li+) or larger (Cs+) than K+ show negligible activation, whereas ions with radii differing only approximately 0.1 A from that of K+ (NH4+ and Rb+) activate to approximately half the turnover rate observed with K+. Single turnover experiments with Hsc70 demonstrate that ATP hydrolysis is 5-fold slower with Na+ than with K+. The equilibrium binding of ADP or ATP to Hsc70 is unperturbed when K+ is replaced with Na+. These results are consistent with a role for monovalent ions as specific cofactors in the enzymatic hydrolysis of ATP.     

Menstrual and reproductive factors and risk of breast cancer in Asian-Americans

We conducted a population-based case-control study of breast cancer among Chinese-, Japanese- and Filipino-American women in Los Angeles County Metropolitan Statistical Area (MSA), San Francisco-Oakland MSA and Oahu, Hawaii. One objective of the study was to quantify breast cancer risks in relation to menstrual and reproductive histories in migrant and US-born Asian-Americans and to establish whether the gradient of risk in Asian-Americans can be explained by these factors. Using a common study design and questionnaire in the three study areas, we successfully conducted in-person interviews with 597 Asian-American women diagnosed with incident, primary breast cancer during the period 1983-87 (70% of those eligible) and 966 population-based controls (75% of those eligible). Controls were matched to cases on age, ethnicity and area of residence. In the present analysis, which included 492 cases and 768 controls, we observed a statistically non-significant 4% reduction in risk of breast cancer with each year delay in onset of menstruation. Independent of age at menarche risk of breast cancer was lower (odds ratio; OR=0.77) among women with menstrual cycles greater than 29 days. Parous Asian-American women showed a significantly lower risk of breast cancer then nulliparous women (OR=0.54). An increasing number of livebirths and a decreasing age at first livebirth were both associated with a lower risk of breast cancer, although the effect of number of livebirths was no longer significant after adjustment for age at first livebirth. Women with a pregnancy (spontaneous or induced abortions) but no livebirth had a statistically non-significant increased risk (OR=1.84), but there was no evidence that one type of abortion was particularly harmful. A positive history of breastfeeding was associated with non-significantly lower risk of breast cancer (OR=.78). There are several notable differences in the menstrual and reproductive factors between Asian-Americans in this study and published data on US whites. US-born Asian Americans had an average age at menarche of 12.12 years-no older than has been found in comparable studies of US whites, but 1.4 years earlier than Asian women who migrated to the US. Asian-American women, particularly those born in the US and those who migrated before age 36, also had a later age at first birth and fewer livebirths than US whites. A slightly higher proportion of Asian-American women breastfed, compared with US whites. The duration of breastfeeding was similar in US-born Asians and US whites, but was longer in Asian migrants, especially those who migrated at a later age. Menstrual and reproductive factors in Asian-American women are consistent with their breast cancer rates being at least as high as in US whites, and they are. However, the effects of these menstrual and reproductive factors were small and the ORs for migration variables changed only slightly after adjustment for these menstrual and reproductive factors. These results suggest that the lower rates of breast cancer in Asians must be largely as a result of other environmental/lifestyle factors.     

Colour duplex ultrasonography in the rational management of chronic venous leg ulcers

Colour duplex ultrasonographic imaging has largely replaced venography in the assessment of lower-limb venous disorders. This is a study of the use of duplex in the management of patients with chronic venous ulceration in community ulcer clinics. Patients with chronic leg ulceration and an ankle: brachial pressure index of 0.85 or greater were studied. Assessment of venous competence in both the deep and superficial systems of the affected and unaffected legs was performed using colour venous duplex imaging. Reflux was defined as reverse flow for greater than 1 s after manual calf compression. One hundred consecutive patients were assessed over 15 months. Of 111 ulcerated legs, 96 had active ulceration, while 15 had been ulcerated within the previous 6 months. Fifty-seven (51 per cent) of the 111 ulcerated legs had superficial incompetence alone (88 per cent long saphenous system or its perforators, 12 per cent short saphenous system). Six legs (5 per cent) had isolated deep venous incompetence. Forty-two legs had mixed superficial and deep venous reflux; 22 of these had undergone previous venous surgery. Colour venous duplex assessment demonstrated superficial venous disease in approximately half of limbs with chronic leg ulceration. Venous dysfunction in these patients is potentially curable by surgery.     

Acute hypoxemia depresses the cardiorespiratory response during phase I constant load exercise and unloaded cycling

The effects of acute inhalation of hypoxic gas mixtures on minute ventilation (VE), respiratory frequency (fR) and heart rate (HR) were studied in healthy subjects executing constant-load 100 W and 150 W hindlimb exercises (protocol 1) or unloaded (0 W) cycling (protocol 2). Attention was focussed on early changes in variables during phase I of constant load exercise, a period where neurogenic afferents from working muscles play a key role in adaptative cardiorespiratory response as they did also during 0 W cycling. In protocol 1, a 15% O2 gas mixture was used while in protocol 2, 15% and 10% O2 mixtures were tested. Compared to the variations of cardiorespiratory variables measured during room air breathing (normoxia), hypoxemia significantly and markedly depressed the rates of VE and fR changes during phase I exercise but did not affect the changes in HR. Reduced phase I ventilatory response was not accompanied by significant variations in rest values of PaCO2 and pHa associated with the response to hypoxia. The cardiorespiratory response to 0 W cycling was also lowered under hypoxemic conditions, the magnitude of VE and HR changes being inversely proportional to the fall in PaO2 level. Based on electrophysiological animal observations, the present results may be interpreted in terms of inhibitory influences of hypoxemia on proprioceptive muscle afferents.     

Transportin: nuclear transport receptor of a novel nuclear protein import pathway

The main purposes of this study were to investigate the best parameter for describing gallbladder emptying and whether gallbladder bile emptying should be induced with a bolus injection or continuous infusion of cholecystokinin-octapeptide (CCK-8). METHODS: Gallbladder emptying was measured by dynamic cholescintigraphy. Twelve healthy subjects and six patients with gallstones were examined twice with CCK-8 infusion cholescintigraphy, 0.3 ng CCK-8 kg per min for 60 min under identical circumstances. Another six healthy subjects randomly received bolus injection (0.04 microgram/kg) and infusion of CCK-8 (0.3 ng/kg per min for 60 min), respectively, during cholescintigraphy on two separate occasions. The choice of bolus dose was based on recommendations from the CCK-8 manufacturer. The infusion dose was chosen to produce plasma CCK concentrations similar to postprandial plasma CCK levels. RESULTS: A parameter of gallbladder emptying, mean ejection fraction (EF), was defined as 100% minus the area under the time-activity curve normalized to 100% and divided by the time interval from maximum to minimum counts per minute. This parameter proved superior to the well known parameters, EFmax. and EF30, in regard to reproducibility in healthy subjects. The slope of the regression line for the mean EF was 0.998 and the intercept value approximately 0% (p = 0.0001). The mean coefficient of variation was 4%. Apart from a higher mean coefficient of variation, similar reproducibility results were seen in the six patients. The measurements of EF30 in healthy subjects scattered more widely around the mean compared to the mean EF and EFmax, which indicates poorer ability to separate normal from abnormal gallbladder emptying. Intravenous bolus injection of CCK-8 resulted in incomplete gallbladder emptying with a mean EF value of 16% (s.d. 9%; range 7%-32%) compared to 49% (s.d. 7%; range 37%-57%) following CCK-8 infusion (p = 0.004). Abdominal discomfort was observed in all subjects after administration of the bolus injection, whereas no complaints were reported during infusion. CONCLUSION: Mean EF is the best parameter for describing gallbladder emptying. Moreover, slow infusion of a physiological dose of CCK-8 is preferable to induce gallbladder emptying because it results in more complete emptying and has no side effects.     

Localization of preprogalanin messenger RNA in rat brain: identification of transcripts in a subpopulation of cerebellar Purkinje cells

Galanin, a 29 amino acid peptide, is widely distributed throughout both the peripheral and central nervous systems and is thought to be involved in multiple physiological functions including smooth muscle relaxation, stimulation of feeding, blood pressure regulation, control of hormone secretion and modulation of nociception. Galanin has been shown to co-exist with several neurotransmitters throughout the neuroaxis and in some cases to modify their presynaptic and postsynaptic actions. In the present study, the anatomical distribution of preprogalanin messenger RNA in rat brain was examined by in situ hybridization histochemistry using specific 35S-labelled oligonucleotide probes. Neurons expressing preprogalanin messenger RNA were found throughout the brain and were particularly abundant in the hypothalamus. High densities of preprogalanin messenger RNA-positive neurons were found in the anteroventral preoptic, supraoptic, paraventricular and dorsomedial nuclei of the hypothalamus, in the locus coeruleus and in the nucleus of the solitary tract. Moderate densities of preprogalanin messenger RNA-positive cells were apparent in the periventricular and arcuate nuclei of the hypothalamus, in the dorsal raphe and dorsal cochlear nuclei. Low densities of preprogalanin messenger RNA-expressing neurons were observed in the piriform cortex, medial septum and the retrochiasmatic area. These findings are consistent with results of previous in situ localization studies of preprogalanin messenger RNA and also with studies reporting the distribution of galanin-like immunoreactivity in rat brain. A novel finding, however, was the detection of preprogalanin messenger RNA in Purkinje cells in the caudal cerebellar vermis (lobules 6 to 10) and the flocculus and paraflocculus of the lateral hemispheres of the cerebellum. Galanin is presumably co-localized in these cells with GABA, which is normally present in Purkinje cells and possibly with tyrosine hydroxylase, which has recently been detected in a similar subpopulation of cerebellar Purkinje cells in both rat and mouse. Thus, the present study reveals a previously unreported site of galanin gene expression in the cerebellum which represents a novel, putative site of action for galanin to add to its already varied physiological roles.     

Safety and immunogenicity of Env 2-3, a human immunodeficiency virus type 1 candidate vaccine, in combination with a novel adjuvant, MTP-PE/MF59. NIAID AIDS Vaccine Evaluation Group

We investigated the safety and immunogenicity of a candidate HIV-1 vaccine, Env 2-3 (Chiron Biocine Co.), in combination with an adjuvant emulsion, MF59, with or without an additional immune modulator, MTP-PE 78 healthy HIV-1-seronegative adults. Sixteen subjects participated in a dose escalation study of MTP-PE in MF59 without Env 2-3, given at 0 and 1 months; 48 subjects participated in a study of a fixed dose of 30 micrograms of Env 2-3 in MF59 with increasing doses of MTP-PE (0, 5, 10, 25, 50, and 100 micrograms), and 14 subjects participated in a study of 100 micrograms of Env 2-3 in MF59 without MTP-PE. Subjects were assigned to study groups under a randomized, double-blind allocation. Subjects received immunization at 0, 1, and 6 months, and had the option of receiving a fourth dose at 12-18 months. Env 2-3 in MTP-PE/MF59 was associated with significant reactogenicity, in that severe, although self-limited systemic and/or local reactions occurred in 15 of 30 vaccinees. In contrast, Env 2-3 in MF59 without MTP-PE was relatively well tolerated, and severe local and/or systemic reactions occurred in only 2 of 18 subjects. Env 2-3 stimulated serum antibodies to HIV-1 envelope protein (gp120) as detected by Western blot in 39 of 43 subjects and to HIV-1 virus lysate by EIA in 28 of 43 subjects after three injections. The majority of subjects also developed EIA antibodies to recombinant gp120 (SF-2), gp120 (LAI), and V3 peptide (SF-2). Neutralizing antibodies to the homologous SF-2 strain developed in 30 of 43 and 27 of 34 subjects, and fusion inhibition antibodies in 25 of 43 and 15 of 36 subjects after three and four injections, respectively. Lymphoproliferative responses to the immunogen, Env 2-3 were observed in over 80% of the vaccinees examined, and CD4+ cytotoxic T cell activity directed against HIV-1 was noted transiently in 2 of 20 vaccinees. Addition of MTP-PE to Env 2-3 or increasing the dose of Env 2-3 from 30 to 100 micrograms did not augment immunogenicity. Env 2-3 in MF59 was well tolerated and immunogenic in HIV-1-seronegative individuals. The addition of MTP-PE significantly increased reactogenicity, but had little, if any, effect on immunogenicity.     

Actinic erythema, false innocuousness of UV.A

The number of skin cancers is doubled every ten years. The responsibility of excessive sun exposure is incontestable as much for what concerns spino and baso cellular epitheliomas as for malignant melanomas. Over-exposure to ultraviolet B rays was considered as the determining cause of skin cancer and the entire prevention campaign was limited to the safeguard from these rays only. In reality, ultraviolet B rays are not uniquely responsible. Recent studies show that ultraviolet A rays, previously considered innocuous, are on the contrary aggressive as well and in a very deceiving way: it appears that it is the exposure to these rays in weak but repeated doses which are the most dangerous. It appeared that the visually determined value of MED was unchanged but the minimal dose responsible for color changes detectable with chromameter was decreased in the presence of UV.A for 3 subjects out of 4. This decrease was about 50% of the value obtained with UV.B alone. The strategy of protection needs to be completely reconsidered, particularly because today's lifestyle favors the exposition to ultraviolet A rays. There is an increase in exposure to UV.A rays when protection is limited only against ultraviolet B rays, giving a false sense of security especially to those who frequent tanning salons. It is therefore necessary to limit exposure time, use sunscreens protecting against not only UV.B, but also UV.A rays, and prohibit tanning salons. Public educational measures are inexistant, but should be introduced hastily in all public services.