Convergent evolution of cysteine residues in sperm protamines of one genus of marsupials, the Planigales

A characteristic feature of the sperm P1 protamines of eutherian mammals is the constant presence of six to nine cysteine residues per molecule. During spermiogenesis these residues become oxidized to form a three-dimensional network of disulfide bridges between, and within, protamine molecules in the sperm chromatin. This covalent cross linking strongly stabilizes eutherian sperm nuclei. In contrast, protamines sequenced from teleost fish, birds, monotremes, and marsupials all lack cysteine residues and their sperm nuclei, without the stabilizing cross links, are easily decondensed in vitro. We have now found that one genus of tiny, shrewlike dasyurid marsupials, the Planigales, possess P1 protamines containing five to six cysteine residues. These residues appear to have evolved since the divergence of Planigales from other members of the family Dasyuridae, such as the marsupial mouse, Sminthopsis crassicaudata. We believe this constitutes a case of convergent evolution in a subfamily of dasyurid marsupials toward the cysteine-rich eutherian form of sperm protamine P1.      

Prognostic trees to aid prognosis in patients with cutaneous malignant melanoma. Scottish Melanoma Group.

OBJECTIVES--To design user friendly guides to prognosis for patients who have had invasive primary cutaneous malignant melanomas surgically excised. DESIGN--Adaptation of the classification tree method was used to derive prognostic trees for four different subgroups of malignant melanoma patients in whom known and possible prognostic variables interacted in different ways. SETTING--Scotland. SUBJECTS--Statistical modelling for prognostic trees was based on 1978 patients whose primary malignant melanoma was first diagnosed in 1979-86 for whom five year follow up and all relevant clinical pathological data were available. The resultant model was validated with 300 patients first diagnosed in 1987 for whom the same information was available. MAIN OUTCOME MEASURES--Actual and predicted rate of survival after diagnosis of primary cutaneous malignant melanoma. RESULTS--The four subgroups of patients were men and women with ulcerated and non-ulcerated cutaneous primary melanomas. Validation of the model showed excellent agreement between actual status of patients in the relevant subgroups and their status as predicted by the model. CONCLUSIONS--The prognostic trees are simple to use and give more accurate prognosis for individual patients than is currently available from tumour thickness alone.     

Measured bronchodilator use in preschool children with asthma.

OBJECTIVE--To investigate how parents use bronchodilator treatment for relief of symptoms when treating their asthmatic preschool children. DESIGN--A commercial electromechanical timer device was attached to a large volume spacer to record the time and date of each use of inhaled bronchodilator over two months. The recorded time and dates were compared with symptoms noted in an asthma diary card. SETTING--Large paediatric teaching hospital in Glasgow. SUBJECTS--29 preschool children with moderately severe asthma attending a specialist paediatric asthma clinic. MAIN OUTCOME MEASURES--Inhaler use measured by the timer device; symptoms and inhaler use recorded by parents in a daily asthma diary. RESULTS--Satisfactory data were obtained in 22 of the 29 children; the median number of study days was 53 (range 18-77). Asthmatic symptoms were recorded on a median of 30 (3-77) days. Bronchodilator was used on a median of 19 (2-73) days, or on 63% (7-100%) of days when symptoms occurred. The median number of puffs used in a day was 1 (range 0-100) and was significantly related to symptom severity in only 14 of the 22 children. In only two of the 22 children was bronchodilator given more frequently than four hourly, and only five children ever used more than 12 puffs a day. CONCLUSIONS--The frequency of parental administration of bronchodilator treatment was variable and not closely related to the parent''s record of symptom severity. Parents often recorded symptoms in their children but did not treat them.     

Specific Binding of the Karyopherin Kap121p to a Subunit of the Nuclear Pore Complex Containing Nup53p,Nup59p,and Nup170p

We have identified a specific karyopherin docking complex within the yeast nuclear pore complex (NPC) that contains two novel, structurally related nucleoporins, Nup53p and Nup59p, and the NPC core protein Nup170p. This complex was affinity purified from cells expressing a functional Nup53p–protein A chimera. The localization of Nup53p, Nup59p, and Nup170p within the NPC by immunoelectron microscopy suggests that the Nup53p-containing complex is positioned on both the cytoplasmic and nucleoplasmic faces of the NPC core. In association with the isolated complex, we have also identified the nuclear transport factor Kap121p (Pse1p). Using in vitro binding assays, we showed that each of the nucleoporins interacts with one another. However, the association of Kap121p with the complex is mediated by its interaction with Nup53p. Moreover, Kap121p is the only β-type karyopherin that binds Nup53p suggesting that Nup53p acts as a specific Kap121p docking site. Kap121p can be released from Nup53p by the GTP bound form of the small GTPase Ran. The physiological relevance of the interaction between Nup53p and Kap121p was further underscored by the observation that NUP53 mutations alter the subcellular distribution of Kap121p and the Kap121p- mediated import of a ribosomal L25 reporter protein. Interestingly, Nup53p is specifically phosphorylated during mitosis. This phenomenon is correlated with a transient decrease in perinuclear-associated Kap121p.     

Thymocyte/stromal cell chimaerism in allothymus-grafted Xenopus: developmental studies using the X. borealis fluorescence marker

These experiments employ the X. borealis (quinacrine-fluorescence) cell marker to illustrate that froglet (normal or in vivo-irradiated) thymuses, alloimplanted to 4- to 6-week-old, 7-day-thymectomized hosts, become filled with host lymphoid cells, while a range of thymic stromal cell types (e.g. epithelial derivatives and reticuloendothelial cells) remain donor derived. A time-course study of 4 micron historesin-embedded sections reveals that for normal thymus implants, host cells begin to immigrate in good number only after metamorphosis. In contrast, 3000 rad-irradiated thymus implants begin to be repopulated with host lymphocytes within 2 weeks postimplantation, when hosts are still at a late larval stage of development. Despite rapid colonization by host lymphoid cells, irradiated thymuses remain small and often disappear in early adult life. Donor-derived lymphocytes frequent the blood and both the red pulp and perifollicular regions of the spleen following normal thymus implantation, whereas such thymic emigrants were not seen in the periphery of thymectomized hosts grafted with irradiated thymus glands.     

Inp1p is a peroxisomal membrane protein required for peroxisome inheritance in Saccharomyces cerevisiae

Cells have evolved molecular mechanisms for the efficient transmission of organelles during cell division. Little is known about how peroxisomes are inherited. Inp1p is a peripheral membrane protein of peroxisomes of Saccharomyces cerevisiae that affects both the morphology of peroxisomes and their partitioning during cell division. In vivo 4-dimensional video microscopy showed an inability of mother cells to retain a subset of peroxisomes in dividing cells lacking the INP1 gene, whereas cells overexpressing INP1 exhibited immobilized peroxisomes that failed to be partitioned to the bud. Overproduced Inp1p localized to both peroxisomes and the cell cortex, supporting an interaction of Inp1p with specific structures lining the cell periphery. The levels of Inp1p vary with the cell cycle. Inp1p binds Pex25p, Pex30p, and Vps1p, which have been implicated in controlling peroxisome division. Our findings are consistent with Inp1p acting as a factor that retains peroxisomes in cells and controls peroxisome division. Inp1p is the first peroxisomal protein directly implicated in peroxisome inheritance.     

Proteomic and genomic characterization of chromatin complexes at a boundary

We have dissected specialized assemblies on the Saccharomyces cerevisiae genome that help define and preserve the boundaries that separate silent and active chromatin. These assemblies contain characteristic stretches of DNA that flank particular regions of silent chromatin, as well as five distinctively modified histones and a set of protein complexes. The complexes consist of at least 15 chromatin-associated proteins, including DNA pol epsilon, the Isw2-Itc1 and Top2 chromatin remodeling proteins, the Sas3-Spt16 chromatin modifying complex, and Yta7, a bromodomain-containing AAA ATPase. We show that these complexes are important for the faithful maintenance of an established boundary, as disruption of the complexes results in specific, anomalous alterations of the silent and active epigenetic states.     

A comparison of physiological responses and rating of perceived exertion between high-impact and low-impact aerobic dance sessions

The aim of this study was to compare the exercise intensity and rating of perceived exertion (RPE) of a high-impact (HIP) and a low-impact (LIP) university aerobic dance session. Ten women [mean (SD) age 22.9 (2.6) years] took part in the study. An incremental treadmill test was performed by each subject to determine maximum oxygen consumption (V˙O_{2 max} ) and maximum heart rate (HR _max ). The measured V˙O_{2 max} [mean (SD)] was 49.0 (7.5) ml · kg⁻¹ · min⁻¹. The subjects were randomly assigned to LIP and HIP sessions (i.e. five of the subjects participated in the HIP session first, and the other five participated in the LIP session first). In a laboratory, heart rate, oxygen uptake and RPE were measured throughout each session for each subject. Expired air was collected continuously throughout the sessions using Douglas bags (ten bags over a 30-min period). The sessions consisted of 20 min of aerobic exercise (bags 1–7) followed by 5 min of local muscular endurance exercise (bags 8 and 9) and 5 min of flexibility exercises (bag 10). The mean intensity of the aerobic section of the LIP and HIP sessions was 51.6% and 64.7% V˙O_{2 max} , respectively. Ninety-five percent confidence intervals for the average difference between the HIP and LIP sessions demonstrate that the %V˙O_{2 max} was between 12% and 14% higher for the HIP session. The mean %HR _max for the LIP and HIP sessions was 71.4% and 76.7%, respectively, with the %HR _max in the HIP session being between 5.4% and 7.2% higher on average than that of the LIP session. On average, the RPE for the aerobic section of the HIP session (12.1) was consistently higher than that of the LIP session (11.1). HIP activity has the potential to maintain/improve the aerobic fitness of its participants. According to the literature, the exercise intensity elicited by LIP activity may have a limited training effect for the population utilised in this study, and for some individuals may result in detraining. Conversely, LIP activities may be an appropriate mode of exercise for overweight and unfit individuals. Accepted: 5 January 1998