Fission yeast pak1+ encodes a protein kinase that interacts with Cdc42p and is involved in the control of cell polarity and mating

A STE20/p65pak homolog was isolated from fission yeast by PCR. The pak1+ gene encodes a 72 kDa protein containing a putative p21-binding domain near its amino-terminus and a serine/threonine kinase domain near its carboxyl-terminus. The Pak1 protein autophosphorylates on serine residues and preferentially binds to activated Cdc42p both in vitro and in vivo. This binding is mediated through the p21 binding domain on Pak1p and the effector domain on Cdc42p. Overexpression of an inactive mutant form of pak1 gives rise to cells with markedly abnormal shape with mislocalized actin staining. Pak1 overexpression does not, however, suppress lethality associated with cdc42-null cells or the morphologic defeat caused by overexpression of mutant cdc42 alleles. Gene disruption of pak1+ establishes that, like cdc42+, pak1+ function is required for cell viability. In budding yeast, pak1+ expression restores mating function to STE20-null cells and, in fission yeast, overexpression of an inactive form of Pak inhibits mating. These results indicate that the Pak1 protein is likely to be an effector for Cdc42p or a related GTPase, and suggest that Pak1p is involved in the maintenance of cell polarity and in mating.     

Primary pneumococcal peritonitis complicated by exudative pleural effusion in an adolescent girl

A healthy, young adolescent girl developed primary pneumococcal peritonitis, an infection rarely reported in this age group in North America. Her course was further complicated by exudative pleural effusion and pneumonia despite receiving 10 days of clindamycin therapy. Laparascopy proved useful in making the initial diagnosis, but may have contributed to the pathogenesis of the pulmonary process. Case presentation, management, and etiology are discussed.     

Mapping of a yeast G protein betagamma signaling interaction

The mating pathway of Saccharomyces cerevisiae is widely used as a model system for G protein-coupled receptor-mediated signal transduction. Following receptor activation by the binding of mating pheromones, G protein betagamma subunits transmit the signal to a MAP kinase cascade, which involves interaction of Gbeta (Ste4p) with the MAP kinase scaffold protein Ste5p. Here, we identify residues in Ste4p required for the interaction with Ste5p. These residues define a new signaling interface close to the Ste20p binding site within the Gbetagamma coiled-coil. Ste4p mutants defective in the Ste5p interaction interact efficiently with Gpa1p (Galpha) and Ste18p (Ggamma) but cannot function in signal transduction because cells expressing these mutants are sterile. Ste4 L65S is temperature-sensitive for its interaction with Ste5p, and also for signaling. We have identified a Ste5p mutant (L196A) that displays a synthetic interaction defect with Ste4 L65S, providing strong evidence that Ste4p and Ste5p interact directly in vivo through an interface that involves hydrophobic residues. The correlation between disruption of the Ste4p-Ste5p interaction and sterility confirms the importance of this interaction in signal transduction. Identification of the Gbetagamma coiled-coil in Ste5p binding may set a precedent for Gbetagamma-effector interactions in more complex organisms.     

Effects of preliminary muscular exercise on body temperature, water loss and physical performance

We investigated the effects of preliminary exercise (muscular warm-up) on body temperature, water loss and physical performance during consecutive sustained exercise. Thirty-one untrained men aged 21 to 30 years old (mean 25.12 +/- 2.92) were subjected to two physical trial tests at 75% Pma. One trial. (T - PE) was performed without preliminary exercise (PE) and the other (T + PE) was preceded by 15 minutes of preliminary exercise performed at 50% Pma. The trials involved pedaling an ergocycle until exhaustion, followed by a 30 minutes period of inactive recovery. The rate of increase of body temperature during the work consecutive to preliminary exercise (T + PE) was lower than that of the work without preliminary exercise (T - PE). The energy output and water loss during T + PE were significantly (P < 0.01) greater than during T - PE. However, the body temperatures at the end of the two tests were identical. The rate of decrease of body temperature, measured after 30 minutes of recovery, was higher for T + PE than T - PE. The duration of work was increased by PE for 25 (80.65%) subjects and decreased for 6 (19.35%). We conclude that preliminary exercise allows better adjustment of thermohydric regulation by moderating the rise in body temperature and increasing water loss during physical work. For most subjects, these adjustments allow improved endurance.     

Water filtration of the forearm in short- and long-term diabetes mellitus

Blood flow and capillary filtration coefficient (CFC) were measured by strain-gauge plethysmography on the upper and lower third of the forearm in 9 normal subjects and 29 well regulated patients with diabetes mellitus of varying duration (less than 10 years, 10 to 20 years, and more than 20 years). There was no difference in blood flow in the four groups, but CFC was significantly increased in long-term diabetes (duration above 20 years) when measured at the distal part of the forearm near the wrist. Calculations showed that this was probably due to the relatively high contribution of connective tissue in this part of the forearm. Increased water filtration in connective tissue in long-term diabetics is in accordance with earlier findings of a lowered subcutaneous interstitial fluid albumin concentration in long-term diabetics, this being explained by an increase in net water outflux from the microcirculation.