Smoking status of parents, siblings and friends: predictors of regular smoking? Findings from a longitudinal twin-family study.

The relationship between regular smoking behavior and the smoking behavior of parents, siblings and friends was investigated using data from the Netherlands Twin Register. Cross-sectional analyses of data of 3906 twins showed significant associations between smoking behavior of the participant and smoking behavior of co-twin, additional brothers, parents of the same sex as the participant and friends. Those variables, together with age, explained 47% of the variance in smoking behavior. Longitudinal analyses of data from 2397 twins, who, in 1993, reported never to have smoked (regularly), showed that uptake of regular smoking two years later was predicted by having a smoking co-twin, smoking same-sex siblings, smoking mother and smoking friends. Males are, in contrast to females, at a later age still vulnerable to taking up regular smoking. The variables explained 21% of the variance. Sport participation, alcohol use, boredom susceptibility and neuroticism significantly added to the predictive value of this model. Including those additional factors increased the explained variance to 30%, and subsequently adding experimental smoking behavior further increased the explained variance to almost 50%. In summary, having smoking family members and friends, as well as lifestyle and personality factors are important predictors for the uptake of regular smoking. However, the experimental smoking behavior of the participant is equally important.     

Differential distribution of rat PDE-7 mRNA in embryonic and adult rat brain

Currently not much is known about the distribution and function of the phosphodiesterase type 7 (PDE-7) enzyme. Therefore, we carried out an extensive distribution analysis of the rat and human PDE-7 byin situ hybridization as well as RT-PCR. We isolated a partial rat cDNA clone that is highly homologous to the sequence of the human PDE-7 gene. RT-PCR tissue distribution analyses revealed expression of the mRNA of the human and rat-enzymes in most of the examined tissues, like adult heart, lung, brain, and liver, as well as in several cell lines of the immune system.In situ hybridization with the rat PDE-7 showed a differential expression pattern during the late phases of the developing rat brain with higher levels of mRNA in cortical and telencephalic structures in d 16, 18 and 20 embryonic stages, whereas in adult rat brain, higher amounts of mRNA could only be detected in cerebellum and, to a lesser extent, in hippocampus and the olfactory system.     

High yield fermentation and purification of Tendamistat disulphide analogues secreted by Streptomyces lividans

In our studies of structure-function correlation of polypeptides we used Tendamistat (TM), an -amylase-inhibitor of Streptomyces tendae, as a model to investigate the influence of different mutants on the expression and secretion of the protein. In addition, we examined the influence of replacing the two disulphide-bridges that stabilize the two-loop structure of the whole protein. The single mutants C27S, C27T, C45A, the double mutants C11A/C27A, C11A/C27S, C11A/C27T, C11A/C27L, C45/C73A and the fourfold mutant C11A/C27A/C45A/C73A were prepared. The mutated TM gene was expressed in S. lividans TK 24, which secretes the active form of the inhibitor into the culture medium. Compared with the wild-type, the double-mutated TM derivatives show an increase in secreted protein by a factor of two to ten. In contrast, the single-mutated inhibitor analogues show the reverse effect. In order to examine the influence of temperature and culture media on the production of protein derivative we used the most unstable C11A analogue. Our expression studies at 10, 19, 28 and 37° C established 19° C as the optimal temperature for production of the protein derivatives. The correlation between the stability and secretion of TM is discussed in the context of our knowledge of protein translocation in bacteria. Based on these experiments we optimized the fermentation parameters, isolated TM analogous on a large scale, and verified them. Correspondence to: J. W. Engels     

Measurement of intracellular collagen degradation

Intracellular degradation of newly synthesized collagen is quantitated by incubating fibroblasts with [¹⁴C]proline and determining the percentage of total [¹⁴C]hydroxyproline that is present in a low molecular weight fraction. Several problems make this difficult. (1) Commercial [¹⁴C]proline is often contaminated with [¹⁴C]hydroxyproline and must be purified before use. (2) Salt and [¹⁴C]proline interfere with the determination of [¹⁴C]hydroxyproline in the low molecular weight fraction and must be removed by preparative ion-exchange chromatography. (3) Epimerization of trans- to cis-hydroxyproline during acid hydrolysis is variable and must be taken into account. (4) Loss of [¹⁴C]hydroxyproline during processing varies; [³H]hydroxyproline can be used as an internal measure of recovery, even though tritium may be lost during hydrolysis. An analytic cation-exchange resin is used for the final quantitation of [¹⁴C]hydroxyproline in the low and high molecular weight fractions. With these methods, degradation of newly synthesized collagen can be determined with a precision of ± 3%.     

Characters that differ between diploid and haploid honey bee (Apis mellifera) drones

Diploid males have long been considered a curiosity contradictory to the haplo-diploid mode of sex determination in the Hymenoptera. In Apis mellifera, 'false' diploid male larvae are eliminated by worker cannibalism immediately after hatching. A 'cannibalism substance' produced by diploid drone larvae to induce worker-assisted suicide has been hypothesized, but it has never been detected. Diploid drones are only removed some hours after hatching. Older larvae are evidently not regarded as 'false males' and instead are regularly nursed by the brood-attending worker bees. As the pheromonal cues presumably are located on the surface of newly hatched bee larvae, we extracted the cuticular secretions and analyzed their chemical composition by gas chromatograph-mass spectrometry (GC-MS) analyses. Larvae were sexed and then reared in vitro for up to three days. The GC-MS pattern that was obtained, with alkanes as the major compounds, was compared between diploid and haploid drone larvae. We also examined some physical parameters of adult drones. There was no difference between diploid and haploid males in their weight at the day of emergence. The diploid adult drones had fewer wing hooks and smaller testes. The sperm DNA content was 0.30 and 0.15 pg per nucleus, giving an exact 2:1 ratio for the gametocytes of diploid and haploid drones, respectively. Vitellogenin was found in the hemolymph of both types of imaginal drones at 5 to 6 days, with a significantly lower titer in the diploids.     

OBSERVATIONS ON FILAMENT FORMATION IN MICRASTERIAS FOLIACEA (DESMIDIACEAE,CHLOROPHYTA)1

Filaments of Micrasterias foliacea Bailey were isolated from a sample of a Texas lake. Cultures were established and examined by light and scanning electron microscopy (SEM). Enzymatic removal of mucilage proved necessary to obtain well preserved cells for SEM investigation. The development of the overlapping polar lobes and the formation of the interlocking apical teeth are described. The importance of these, of mucilage and the primary wall for filament formation is discussed.