Genetics of the quantitative Lp(a) lipoprotein trait

Summary Lp(a) glycoprotein exhibits an apparent size polymorphism that is associated with genetically controlled Lp(a) lipoprotein concentrations in plasma (Utermann et al. 1988). We have tested the hypothesis that this polymorphism is genetically controlled by studying 15 matings with a total of 44 offspring. This confirmed our conclusion that Lp(a) types are controlled by a series of codominant alleles Lp^F, Lp^B, Lp^S1, Lp^S2, Lp^S3 and Lp^S4 and by a null allele Lp^o. Together with the data from the accompanying paper this indicates that the structural gene for the Lp(a) protein is the major gene locus determining Lp(a) lipoprotein concentrations in plasma.     

Photosynthesis and apparent affinity for dissolved inorganic carbon by cells and chloroplasts of Chlamydomonas reinhardtii grown at high and low CO2 concentrations

Chloroplasts with high rates of photosynthetic O₂ evolution (up to 120 mol O₂· (mg Chl)^-1·h^-1 compared with 130 mol O₂· (mg Chl)^-1·h^-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO₂ concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O₂ uptake could be observed in the dark by high- and low-CO₂ adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m^-2·s^-1 for high- and low-CO₂ adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO₂ adapted chloroplasts, whereas high-CO₂ adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O₂ evolution (K_m(DIC)) was 31.1 and 156 M DIC for low- and high-CO₂ adapted chloroplasts, respectively. These results demonstrate that the CO₂ concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl chlorophyll - DIC dissolved inorganic carbon - K_m(DIC) coneentration of dissolved inorganic carbon required for the rate of half maximal net O₂ evolution - PFR photon fluence rate - SPGM silicasol-PVP-gradient medium     

Inactivation of recombinant plasmid DNA from a human erythropoietin-producing mouse cell line grown on a large scale

Summary Experiments were carried out to assess the survival of recombinant plasmid DNA during large-scale production of recombinant human erythropoietin (rhuEPO) in a fermentation pilot plant. The analyses revealed DNA-degrading activities in the fermentation broth and in the waste-water, leading to rapid destruction of plasmid DNA added to medium or waste-water. The capability of the plasmid-DNA-spiked samples to transform competent bacteria was drastically reduced. The DNA-degrading activity in the waste-waters could be blocked by addition of EDTA or by boiling, indicating the presence of DNA-degrading enzymes (DNases). No plasmid-specific DNA sequences were detected in waste-water samples by in-vitro amplification with Taqpolymerase. Genomic DNA preparations of cell debris collected from waste-water samples only contained degraded plasmid DNA. Furthermore, it was shown that intact plasmid DNA could be degraded to fragments of less than 1000 bp by incubation at 121°C for 20 min, leading to a decrease in the plasmid-specific transforming capacity by a factor of 10³ per minute. Thus, DNA from the rhuEPO production pilot plant was efficiently inactivated at three different levels: (i) in the fermentation medium (DNase), (ii) in the waste-water container (DNase), and (iii) by heat inactivation for 20 min at 120°C. These results indicate that the probability of delivery of recombinant DNA into the environment is extremely low in such biotechnological production processes. Offprint requests to: M. R. Fibi     

Modulation of the beta-adrenergic response in cultured rat heart cells

Incubation of rocker-cultured neonatal rat heart cells with 3 mM L(+)-lactate led to a sharp increase in the sensitivity of cardiomyocytes to the beta-adrenergic agonist isoprenaline, as measured by their chronotropic response. This effect was accompanied by a reduction in the arachidonic acid content of the total phospholipids. The phospholipase A₂-activator melittin as well as free arachidonic acid induced this supersensitivity to the same degree. On the other hand, the L(+)-lactate-evoked supersensitivity could be blocked by the phospholipase A₂ inhibitors mepacrine and n-bromophenacyl-bromide, suggesting an involvement of phospholipase A₂ in the process of beta-adrenergic sensitization. The sensitizing action of arachidonic acid was blocked by the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid, but not by the cyclooxygenase inhibitor indomethacin. Supersensitivity was likewise evoked by 15-S-hydroxyeicosatetraenoic acid (15-S-HETE), but not by 5-S-HPETE or 5-S-HETE. These findings suggest that the phospholipase A₂-15-lipoxygenase pathway plays a role in the induction of beta-adrenergic supersensitivity in the cultured cardiomyocytes and point to a new physiological role of the lipoxygenase product 15-S-HETE.Abbreviations NDGA nordihydroguaiaretic acid - HETE hydroeicosatetraenoic acid - HPETE hydroperoxyeicosatetraenoic acid     

The Nutrimentary Egg Development of the Mite,Varroa jacobsoni (Acari,Arachnida), an Ectoparasite of Honey Bees

The fine structure of the female gonad of Varroa jacobsoni is described. There are two components: the ovary proper and the so-called lyrate organ. The ovary is the place where oocytes mature, embedded in a supporting tissue composed of two cell types: somacells 1 and somacells 2. The lyrate organ has a nutrimentary function and is comprised of two components: supporting cells and nutritive tissue. The supporting cells are similar to the somacells 2 in that they contain abundant microtubules. The nutritive tissue is an extensive syncytium. It is connected with the oocytes via intercellular bridges, the nutritive cords. Oocytes and nutritive tissue are thought to have derived from common stem cells. From fine structural evidence it is concluded that ribosomes are one of the most important components to be transported via the nutritive cords into the oocytes. However, an increase in number of mitochondria in the middle-stage oocytes may also be a consequence of transport of these organelles from the nutritive tissue into the oocytes. Further characteristics make plausible that the interdependences of oocytes and nutritive tissue are comparable to those found in meroistic ovarioles of insects. The somatic components do not seem to be as important as the follicle cells of insects, however. It is assumed that the evolution of a nutrimentary oogenesis speeds up embryogenesis. Thus, the differentiation of the female gonad of Varroa jacobsoni may have facilitated the species' adaptation to a development completed in a short and limited time within the shelter of the covered brood cell of the bee.     

Phosphate-Activated Glutaminase in the Crude Mitochondrial Fraction (P2 Fraction) from Human Brain Cortex

The kinetics and other properties of phosphate-activated glutaminase have for the first time been studied in the crude mitochondrial fraction (P2 fraction) from human brain. The enzyme is for unexplained reasons inactivated postmortem. The enzyme activity decreases by storing the tissue or homogenate at 37 degrees C. The inactivation is not caused by formation of a dialysable inhibiting compound. No large proteolytic degradation has occurred, since the phosphate-activated glutaminase-like immunoreactive band did not disappear during the storage. The molecular weight of the subunit of the enzyme as determined by immunoblots of sodium dodecyl sulfate-treated homogenates from human brain is estimated to be approximately 64 K. The enzyme has been shown to have a pH optimum of 8.6; it is activated by phosphate, inhibited by glutamate, and partially inhibited by ammonia. Double-inverse plots of enzyme activity against phosphate are concave-upward, and more so in the presence of an inhibitor. The inhibition by glutamate appears to be noncompetitive with the substrate glutamine, and competitive with the activator phosphate. These kinetic properties are not significantly different from our earlier observations concerning phosphate-activated glutaminase from pig brain and pig kidney.     

The "suspicious" gynecologic smear

"Suspicious" gynecologic smears from 842 patients over a seven-year period were analyzed for their causes and outcomes. The frequency of the cytologic diagnosis of "suspicious" ranged between 0.5% in 1979 and 1.44% in 1975 of all smears examined. Review of the smears showed that this classification was used to report a variety of conditions, including equivocal possible precancerous changes as well as the presence of severe inflammation, degenerative or atrophic changes, abnormal glandular cells and metaplasia. The cytologic follow-up, following anti-inflammatory or hormonal therapy, showed a conversion to negative findings in 65.1% of all cases, usually within 12 months. In 294 cases, histologic analysis became necessary, revealing precancerous changes or cancer in 147 patients (17.5% of the study group). Smears of postmenopausal women with suspicious glandular or endometrial cells received special analysis. Significant numbers of such cases had histologic findings positive for malignancy (20% of smears with glandular cells and 21.3% with endometrial cells), as did also smears showing post-irradiative changes (34.6%) or atrophic and degenerative changes (17.1%). Therefore, "suspicious" smears in these groups were considered to indicate an increased risk of malignancy. A regimen for the proper management of cases with "suspicious" smears has been established.     

Action of neurotensin on size, composition, and growth of pancreas and stomach in the rat

Since the gastrointestinal peptide neurotensin has a stimulatory effect on the secretion of the exocrine pancreas and an inhibitory effect on secretion and motility of the stomach, we investigated whether chronic parenteral administration of neurotensin would affect pancreatic and gastric growth. We therefore infused synthetic neurotensin subcutaneously (dose, 43 and 282 pmol X kg-1 X min-1) in 20 Wistar rats for 2 weeks using Alzet osmotic minipumps and compared pancreatic weight, DNA, RNA, protein, lipase, amylase, pancreatic polypeptide and insulin with these parameters in 10 control rats from the same litter with subcutaneously implanted plastic cylinders approximately the size of the minipumps. In another experiment, synthetic neurotensin (836 pmol X kg-1) was injected intraperitoneally three times a day for 3 days in 12 rats. Thereafter, we measured pancreatic DNA and in vitro incorporation of [3H]thymidine into pancreatic DNA. These effects were compared with the actions of caerulein and normal saline. Long term infusion of the high neurotensin dose induced an increase of pancreatic weight (control: 0.87 g, neurotensin: 1.02 g) and of DNA (control: 2.5 micrograms; neurotensin: 3.5 micrograms) and pancreatic polypeptide (control: 2.4 ng; neurotensin: 7.4 ng) contents, whereas pancreatic protein, RNA, amylase and lipase contents were not stimulated. In relation to DNA, these parameters even were significantly depressed. Insulin remained unchanged. Intraperitoneal injection of neurotensin induced an increase of pancreatic DNA content and stimulated [3H]thymidine incorporation into DNA (control: 11 000 dpm/g; neurotensin: 15 800 dpm/g pancreas). Moreover, long-term neurotensin infusion with the high dose led to a rise in protein concentration and an increase in the thickness of the gastric antrum; antral DNA concentration was insignificantly stimulated. Parenteral neurotensin in the doses and at the times administered, led therefore, to hyperplasia of the pancreas and induced growth of the gastric antrum. It is concluded that neurotensin can act as a trophic factor on pancreas and gastric antrum of the rat. It remains to be determined whether this represents a physiological effect of neurotensin.