Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Titan has a methane cycle akin to Earth's water cycle. It has lakes in polar regions, preferentially in the north; dry low latitudes with fluvial features and occasional rainstorms; and tropospheric clouds mainly (so far) in southern middle latitudes and polar regions. Previous models have explained the low-latitude dryness as a result of atmospheric methane transport into middle and high latitudes. Hitherto, no model has explained why lakes are found only in polar regions and preferentially in the north; how low-latitude rainstorms arise; or why clouds cluster in southern middle and high latitudes. Here we report simulations with a three-dimensional atmospheric model coupled to a dynamic surface reservoir of methane. We find that methane is cold-trapped and accumulates in polar regions, preferentially in the north because the northern summer, at aphelion, is longer and has greater net precipitation than the southern summer. The net precipitation in polar regions is balanced in the annual mean by slow along-surface methane transport towards mid-latitudes, and subsequent evaporation. In low latitudes, rare but intense storms occur around the equinoxes, producing enough precipitation to carve surface features. Tropospheric clouds form primarily in middle and high latitudes of the summer hemisphere, which until recently has been the southern hemisphere. We predict that in the northern polar region, prominent clouds will form within about two (Earth) years and lake levels will rise over the next fifteen years.

Cellular mechanisms of rejection and regeneration in peripheral nerve allografts

A model of rejection and regeneration of peripheral nerve allografts in rats is presented. A 2.5-cm segment of 28 right sciatic nerves was transplanted orthotopically from LEW.1W to DA and from DA to LEW.1W. With a microsurgical technique, proximal and distal coaptations were performed. In an autologous control group the same surgical procedure was applied. Evaluation included clinical estimation of motor recovery and macroscopic appearance of the graft, electrophysiological examination, conventional histology, and immunohistology. The latter concentrated on demonstration of monomorphic and polymorphic determinants of MHC class I and II antigens and of macrophages. By functional, electrophysiological, and histological parameters it was demonstrated that after rejection a certain degree of regeneration took place in the allografts. Both rejection and subsequent regeneration were studied in detail by immunohistology. During the course of Wallerian degeneration MHC class I expression on myelin sheaths could be demonstrated. When the rejection response occurred, additional MHC class II expression on myelin sheaths and on vascular endothelial was observed. Recipient specific class I-positive macrophages were infiltrating the graft from the epineurium and the coaptation sites, and were later present at the sites of myelin degradation. At 6 weeks postoperatively donor-specific MHC products were no longer detectable, but recipient-specific Schwann cells were present in the allograft tissue. We conclude that a rejection response renders a peripheral nerve allograft acellular but does not destroy the nerve architecture, still enabling it to function as an axon conduit. The regeneration in the rejected allograft however lacks the positive neurotropic and -trophic influence physiologically provided by viable Schwann cells.

The use of low-level jets by migrating birds

Birds flying at high altitudes have occasionally been observed above mountain areas and the open sea. For the first time the regular occurrence of migrating birds flying within a low-level jet at heights of 5000 to almost 9000 m asl. have now been verified by radar above the Negev desert in southern Israel. Tracks of rather large birds with wing-beat frequencies of 5-6 Hz were measured to have horizontal flight speeds up to 50 m/s. Visual observations, seasonal occurrence, and wing-beat frequencies allowed to associate them with small species of the order Ciconiiformes (mainly Ardeidae) and possibly with members of the Laro-Limicolae group. These wading birds seem prone to continuing nocturnal migration into daytime under favorable conditions and to make use of high wind speeds at sometimes extreme altitudes.

Results of primary nerve repair in the upper extremity

The results of primary repair of peripheral nerve injury in the upper extremity are reported for 143 nerves in 120 patients, with a mean follow-up of 24 months. Normal values for static and moving two-point discrimination were established and related to the person's age. Sensory reeducation was employed routinely in the postoperative rehabilitation program. Moving two-point discrimination recovered to a better level in 61%, the same level in 38%, and a worse level in 1% than static two-point discrimination after nerve repair. Results for digital, median, ulnar, and radial nerve repairs are reported.

Induction of Phytoalexin Synthesis in Soybean. Structure and Reactions of Naturally Occurring and Enzymatically Prepared Prenylated Pterocarpans from Elicitor-Treated Cotyledons and Cell Cultures of Soybean

Using HPLC on a partisil column (5 μm) it was possible to separate two reaction products from an enzyme incubation of dimethylallylpyrophosphate and 3,6a,9-trihydtoxypterocarpan with a particulate fraction from elicitor-treated soybean cotyledons (Harosoy 63) or soybean cell cultures. These two products were identified by MS and 1H-NMR analysis as 2- and 4-dimethylallyltrihydroxypterocarpan. Both compounds also occur as natural products in elicitor-treated soybean cotyledons and to a smaller extent in soybean cell cultures. Introduction of the dimethylallyl substituent into trihydroxypterocarpan increases the fungitoxicity against Cladosporium cucumerinum.

Upon treatment with alkali, solutions of 3,6a,9-trihydroxypterocarpans turn to an intense red colour with λmax around 530 nm. One of the products from 2-DMA-THP could be isolated by reversed phase HPLC. According to its mass spectrum a quinoid structure is proposed for this red pigment

Muscle transfers in brachial plexus lesions

The concept of reconstruction to regain lost function after brachial plexus lesions has to be as broad and complex as possible. We have been exploring wider and more novel clinical concepts at the Clinic of Plastic, Hand, and Reconstructive Surgery at the Medical School of Hannover. Our ideas are supported by experience in 160 patients. We have attempted to combine the use of a vascularized nerve graft and a microvascularly-transferred autologous muscle. Patients undergoing the procedures have included those with late complete root avulsions and no functional return, as well as previously operated cases with poor recovery of biceps, wrist, and forearm function. The surgery is divided into two stages. In the first stage, the ulnar nerve is prepared as a vascularized nerve graft and is sutured to intercostal nerves 3 to 5 or 6. In stage 2, when the Tinel sign reaches the distal ends of the ulnar nerve graft (about six to eight months later), the latissimus dorsi muscle is harvested. The muscle is then placed as far distally as possible in the forearm and sutured to the deep finger flexors and flexor pollicis longus. Proximally, the insertion is performed similarly to Steindler's method. The vessels are connected to the brachial artery and vein and the thoracodorsal nerve is sutured to the graft. This method provides flexion of both the fingers and the elbow.

Brachial plexus injuries: an integrated treatment concept

An integrated concept is presented for the treatment of lesions of the brachial plexus. In such patients, nerve repair is useless as a single method of therapy. Only the combination of nerve repair with both conventional and new methods of muscle and tendon transfer, including the free muscle transplant innervated by vascularized nerve grafts, can give the patient functional use of the paralyzed arm.

Frequency of toxic shock syndrome toxin- and enterotoxin-producing clinical isolates of Staphylococcus aureus

In 183 clinical isolates of Staphylococcus aureus, toxic shock syndrome toxin was detected in 13.7%, enterotoxin A in 20.2%, enterotoxin B in 7.7%, enterotoxin C in 5.5% and enterotoxin D in 3.3%. Seventy-three (39.9%) of the strains were found to produce one or more toxins. Multiple secretion of toxins was rare (< 1% of all strains) except for the combinations enterotoxin A with toxic shock syndrome toxin and enterotoxin A with enterotoxin D. These combinations were observed at significantly higher frequencies (4.9% and 2.2%, respectively) than would have been expected from values calculated from respective individual frequencies (0.88% and 0.06%) (p < 0.0001). In comparison with Staphylococcus aureus strains isolated from miscellaneous material, Staphylococcus aureus blood culture isolates produced enterotoxin D in significantly larger amounts and at higher frequencies (p = 0.01 in both cases). These toxins might play an important pathogenic role in Staphylococcus aureus infections.

Progress in limb and digital replantation: Part B

Progress in micro- or macroreplantation has resulted in higher survival rates of formerly amputated parts. Progress has been made as a result of intensive laboratory training and considerable experience due to the popular application of microsurgical techniques. More amputated digits or limbs may survive because the time of ischemia can be exceeded in using cold storage or perfusion. Homo- or heterodigital vessel transposition, expanded indications for vein graft interposition, as well as heterotopic transplantation allow for extremity preservation even in crush injuries, and in disastrous multiple amputations combined with contusion or avulsion. Nowadays, microvascular digital replantation with vessel anastomosis distal to the distal interphalangeal joint in adults is technically feasible. Finger amputations in children are a prime indication for replantation. Maintenance of extremity length is possible in applying external fixation. Emergency free flaps or compound tissue transfer under the "Urgence differée" condition may provide reliable soft tissue coverage. Secondary reconstruction with regard to bone defects, tendon repair, and eventual nerve grafting have to be aspired, finally leading to an improvement of functional results in daily and leisure activities as well as in early professional readaptation.

The resistance against Listeria monocytogenes and the formation of germinal centers depend on a functional death domain of the 55 kDa tumor necrosis factor receptor

The biological functions mediated by the death domain of the 55-kDa tumor necrosis factor receptor (TNFRp55) in vivo are still elusive. TNFRp55 mutants lacking a functional death domain were expressed in TNFRp55-/- and in TNFRp55+/- mice as transgenes under control of the H-2Kb promoter. Analysis of these animals revealed that signals originating from the TNFRp55 death domain are indispensable for the protection against Listeria monocytogenes, the expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in the spleen and the development of splenic germinal centers. Furthermore, the transgenic coexpression of the TNFRp55 mutants in TNFRp55+/- mice exerts a dominant negative effect on the signaling of the endogenous receptor chains in vivo.

Regeneration of autologous and allogenic nerve grafts in a rat genetic model: preliminary report

The authors report observations concerning rejection and regeneration processes of allogenic peripheral neural tissue, depending on different genetic mismatches in a rat model. Five groups representing different rat strains (n = 100) were subjected to orthotopic grafting of 2.5-cm segments of sciatic nerve. Combinations represented different genetic barriers, including the Major Histocompatibility Complex (MHC), a non-MHC, a subgroup (A) of the MHC, a group representing MHC plus non-MHC, and an autologous control group. Animals were examined after one, two, and 12 weeks; additional evaluations in some of the experimental groups were done at six and eight weeks. Regeneration in varying degrees was evident in all groups at 12 weeks.

Technetium-99m human immunoglobulin (HIG): a new substance for scintigraphic detection of bone and joint infections

Technetium (99m-Tc)-labelled, polyclonal human immunoglobulin (HIG) has been described as a new agent to detect local infection and inflammation. In this study, we tested 99m-Tc HIG in 55 patients with suspected chronic (n = 42) and acute (n = 13) skeletal infection. Diagnosis was proven operatively (n = 44) and clinically (n = 11), including microbiological culture tests (n = 46). A gamma camera scan was performed 4 and 24 hours after I.v. injection of 500 MBq 99m-Tc-HIG. 99m-Tc-HIG scanning achieved a sensitivity of 91% and a specificity of 93%. We found one false negative and five false positive scintigraphic results in 55 patients. No clinical or biochemical side effects were encountered after 99m-Tc-HIG injection. We recommend this technique especially for localisation of low-grade, chronic osteomyelitis. The mechanisms and kinetics of 99m-Tc-HIG, however, are worth investigating more extensively.

Preservation of peripheral nerve grafts with Schwann cell culture medium

Preservation of peripheral nerves may, in the near future, play an important role in reconstructive surgery, especially if recent advances in immunosuppressive therapy are taken into account. Therefore, it has to be investigated whether peripheral nerves can be stored for some time after harvesting without diminishing their regenerative potential. Previous experiments of our group could demonstrate only little benefit of organ storage solution (HTK) or normal saline (NaCl 0.9%) to peripheral nerves when kept at cold ischaemia of 4 degrees C for 32 and 72 hours. In this presentation, we are reporting the results of peripheral nerve storage in Dulbecco's Modified Eagle Medium which has been used for Schwann cell culture. In 30 adult Sprague-Dawley rats, a 2.5 cm segment of the right sciatic nerve was harvested and kept at 4 degrees C for 14, 32, 72, and 120 hours. It was then reimplanted into the donor animal; regeneration quality was assessed clinically, histologically and morphometrically after 6 weeks. Best regeneration results were obtained in the 32 and 72 hour groups; regeneration here was comparable to the normal controls. These results are explained with the positive effect of nerve predegeneration.

Use of beta-hydroxybutyric acid levels in the emergency department

The impact of a new test on the market, the beta-hydroxybutyric acid (BOH) assay, on clinical decision-making in the emergency department (ED) has not been well studied. In this retrospective analysis, we studied the potential benefit of this new test in the ED decision-making process in diabetic patients. BOH levels were measured on all patients who had glucose and acetone levels ordered by the emergency physician during a 3-month period in the ED of a university tertiary referral center. Two groups were analyzed: group 1 was acetone-positive and BOH-positive (n = 13); group 2 was acetone-negative BOH-positive (n = 31). There was no difference between the two groups in terms of gender (p = 0.55) or age (p = 0. 47). The length of stay (p = 0.97) and number of complications (p = 0.89) were also similar between the two groups.

CONCLUSION

This study suggests that in those diabetic patients with a negative acetone test and a positive BOH test, the addition of the positive result on the BOH test may provide additional prognostic information for predicting hospital length of stay and number of in-hospital complications.