A Link between Meiotic Prophase Progression and Crossover Control

During meiosis, most organisms ensure that homologous chromosomes undergo at least one exchange of DNA, or crossover, to link chromosomes together and accomplish proper segregation. How each chromosome receives a minimum of one crossover is unknown. During early meiosis in Caenorhabditis elegans and many other species, chromosomes adopt a polarized organization within the nucleus, which normally disappears upon completion of homolog synapsis. Mutations that impair synapsis even between a single pair of chromosomes in C. elegans delay this nuclear reorganization. We quantified this delay by developing a classification scheme for discrete stages of meiosis. Immunofluorescence localization of RAD-51 protein revealed that delayed meiotic cells also contained persistent recombination intermediates. Through genetic analysis, we found that this cytological delay in meiotic progression requires double-strand breaks and the function of the crossover-promoting heteroduplex HIM-14 (Msh4) and MSH-5. Failure of X chromosome synapsis also resulted in impaired crossover control on autosomes, which may result from greater numbers and persistence of recombination intermediates in the delayed nuclei. We conclude that maturation of recombination events on chromosomes promotes meiotic progression, and is coupled to the regulation of crossover number and placement. Our results have broad implications for the interpretation of meiotic mutants, as we have shown that asynapsis of a single chromosome pair can exert global effects on meiotic progression and recombination frequency

Zustandsregler in Gebäudeleitsystemen

Das hier vorgestellte Verfahren berechnet aus der in einem Raum gemessenen Lufttemperatur mit Hilfe eines Beobachters die Wandtemperaturen. Mit Klimaanlagen die Wandtemperaturen zu regeln, ist deshalb vorteilhaft, weil über 90% der Wärmeenergie in den Wänden gespeichert ist

Thoracic lymphadenopathy due to vascular transformation of lymph node sinuses associated with upper limb edema in a chronic hemodialysis patient with congestive heart failure

BACKGROUND: Vascular transformation of lymph node sinuses (VTLS) is a rare disorder characterized by transformation of lymph node sinuses into endothelium-lined capillary-like channels. This phenomenon was originally discovered by accident whilst examining regional lymph nodes draining cancer. However, it has been found in association with other conditions associated with lympho venous congestion and distension, such as congestive heart failure (CHF) or even lymphoadenopathy alone. CASE REPORT: We describe the clinical case of a male dialysis patient with CHF (secondary to ischemic-hypertensive cardiac failure) who developed gross edema of the upper left limb on the arteriovenous fistula (AVF) side. Edema appeared within a month after carotid endoarteriectomy following approximately twenty years of chronic hemodialysis. Doppler ultrasound with other investigations showed that subclavian and upper cava veins were patent, but revealed many enlarged lymph nodes in the upper left thorax and in the left axilla. Suspicion of lymphoproliferative disease or metastatic involvement was raised and a lymph node biopsy was performed, revealing VTLS. Bone marrow biopsy and abdominal tomographies showed no mass or a proliferative disorder. Based on a hypothesis of an association between upper limb edema and ipsilateral AVF, the AVF was tied. The upper limb edema decreased dramatically within weeks, whilst RRT was continued by means of a central venous catheter. However, a few months later the patient's condition worsened; he developed relapsing pleural effusions and eventually died. Post-mortem examination revealed severe ischemic-calcific cardiopathy and showed that major thoracic and brachial vessels were patent whilst most thoracic and hilar lymph nodes showed VTLS and fibrosis. CONCLUSIONS: We believe that in our patient CHF was the primary cause of thoracic adenomegaly and that CHF, together with venous hypertension at the left fistula's arm, caused ipsilateral limb edema. Thus, adenomegaly due to VTLS could represent an accompanying feature even in upper limb edema in chronic hemodialysis patients. To our knowledge, this is the first report of such an association. In our patient months were "lost" because we thought that limb edema was secondary to the adenomegaly. It is important that clinicians working in dialysis units are aware that when upper limb edema is present, adenomegaly might just be an accompanying symptom, especially in case of concomitant diagnosis of CHF

Abnormal platelet trace amine profiles in migraine with and without aura

Trace amines, including tyramine, octopamine and synephrine, are closely related to classic biogenic amines. In one study, where these substances were found elevated in plasma of migraineurs, it was hypothesized that trace amine metabolism is deranged in migraine. To confirm these findings, we studied, using a multichannel electrochemical high-performance liquid chromatography system, the concentrations of trace amines in platelets of migraine without aura (MoA) and migraine with aura (MA) patients in headache-free period, compared with controls. Platelet concentrations of trace amines, although elevated in both migraine types, showed a different profile in MoA and MA. Octopamine was significantly higher in MoA sufferers (0.69 +/- 0.43 ng/10(8) platelets) compared with both control subjects (0.22 +/- 0.16 ng/10(8) platelets) and MA patients (0.39 +/- 0.37 ng/10(8) platelets). Synephrine was significantly higher in MA patients (0.72 +/- 0.44 ng/10(8) platelets) with respect to both controls (0.33 +/- 0.25 ng/10(8) platelets) and MoA sufferers (0.37 +/- 0.29 ng/10(8) platelets). These results strengthen the hypothesis that tyrosine metabolism is deranged in migraine and may participate in its pathophysiology