A simple test for enhanced guanyl nucleotide exchange in brain adenylate cyclase systems activated by neurotransmitters

The mechanism of receptor-induced activation of adenylate cyclase has been proposed to involve an enhanced exchange of GDP for GTP. The kinetics of this process have not been investigated so far in the brain due to a spontaneous activation of the enzyme by guanyl nucleotides, which precludes the ability to follow receptor-dependent events. We show that it is possible to investigate the mechanism of receptor action in such systems by using a combination of guanosine 5'-(beta-gamma-imino)triphosphate (Gpp(NH)p) and guanosine 5'-(2-O-thio)diphosphate (GDP beta S). In pineal membranes, beta-adrenergic agonists increase the rate of adenylate cyclase activation by 10 or 100 microM Gpp(NH)p about 40-fold (0.023-0.9 min-1 kact) and decrease the inhibitory potency of GDP beta S nearly 1000-fold. As a result, 100 microM GDP beta S which blocks 90% of the activation by 10 microM Gpp(NH)p has no inhibitory effect in the presence of 10 microM Gpp(NH)p and 10 microM noradrenaline or isoproterenol. In caudate nucleus, dopamine does not appear to increase the rate of activation of adenylate cyclase by 10 microM Gpp(NH)p. Nevertheless, 100 microM GDP beta S blocks 90% of the activation by 10 microM Gpp(NH)p but has no inhibitory effects in the presence of dopamine. Thus, one can demonstrate that even weakly activating receptors have the capacity to facilitate a functional exchange of GDP beta S for Gpp(NH)p and measure the efficacy of the interaction between the receptor and the functionally linked guanyl nucleotide subunit.

"Is magnesium depletion the reason for ototoxicity caused by aminoglycosides?"

Aminoglycoside antibiotic drugs may cause ototoxicity and nephrotoxicity. Our hypothesis postulates that aminoglycosides cause ototoxicity by a mechanism of magnesium depletion in the hair cells of the cochlea. The same mechanism maybe responsible for nephrotoxicity caused by aminoglycosides.

The meaning of patient satisfaction with prepaid primary health care in Israel

This paper reports the development of a self-administered Hebrew-language questionnaire for assessing patient satisfaction with primary care in Israel. Four scale measures of patient satisfaction were empirically constructed. These scales pertained to doctor conduct, doctor-patient communication, teamwork, and ease of access. In addition, a single direct question was used to measure overall satisfaction with the care. Ratings of all aspects of care were negatively skewed, with doctor-conduct and doctor-patient communication usually being the most satisfactory aspects and access the least satisfactory. It was shown that different practices, or the same practice at different points in time, can easily and meaningfully be compared, using mean satisfaction scores, measures of standard deviation, or percentages in each practice with ratings above (or below) the overall mean of all practices. The use of specific measures of patient satisfaction for comparison and intervention is discussed.

The Community Project: the teaching implications of applied epidemiology

The use of the epidemiological method in primary health care (PHC) has become an accepted part of the service. The team will utilize community-oriented data in order to assess the health needs of the population, perform continued surveillance of changes in the health of the people served and for service evaluation. This development in health services has to find its counterpart in the training programme for the future doctor. This paper describes a 6-year experience with a community project carried out in the framework of a clinical clerkship in Family and Community Medicine. The students were able to define the project, collect the data and analyse it, and frequently see the start of the implementation of the recommendations.

Health-related behavior in Israel adolescents

Eight hundred and four high school students were interviewed about selected health-related behaviors in an effort to determine the interrelationships of these characteristics. We found the age of onset and present use of cigarettes by the adolescents to be positively correlated to their use of hashish and having sexual intercourse. The use of hashish and having sexual intercourse were also positively related with each other and the use of hashish to drinking alcohol.

Relation between HLA-B27 and clinical features in patients with acute anterior uveitis

Twenty-six patients with acute anterior uveitis associated with HLA-B27 antigen were compared with 31 patients with acute anterior uveitis HLA-B27 negative. No statistical difference was found in the clinical picture of both groups except for the occurrence of unilateral or bilateral involvement. Almost all patients with bilateral eye involvement were HLA-B27 negative and had no evidence of systemic disease, while unilateral involvement occurred in both groups of HLA-B27 positive and negative patients.

Performance of a new type of blood oxygenator

A new type of direct-contact oxygenator has been tested satisfactorily on dogs in nine experiments. It is based on the principle of the "packed column" and has the advantage of a small hold-up (meaning a small priming volume), no formation of foam, and gentle flowing of the blood. The apparatus is simple enough to be commercially available at a low price and discarded after use. Both PO2 increase and PCO2 decrease were satisfactory and plasma hemoglobin values remained low after 75 minutes of perfusion. Preliminary in vitro experiments on ox and human blood showed a low degree of blood damage.