Neurofilament light chain: A novel blood biomarker in patients with ataxia telangiectasia.

AIM: Neurofilament light chain (NfL) is recognized as a blood biomarker in several neurodegenerative disorders, but its possible relevance in Ataxia Telangiectasia (A-T) has not been examined. The aim of this study was to investigate the biomarker potential of blood NfL concentrations in patients with A-T. METHOD: Blood (serum/plasma) NfL concentrations were measured in a Dutch and an American cohort of patients with A-T and compared to control values. Additionally, correlations between NfL concentrations and disease phenotype (classic versus variant A-T) were studied. RESULTS: In total 40 (23 Dutch and 17 American) patients with A-T (32 patients with classic A-T and 7 patients with variant A-T) and 17 age- and gender-matched (to the American cohort) healthy controls were included in this study. Blood (serum/plasma) NfL concentrations in patients with classic A-T and age ≤ 12 years were elevated compared to age matched controls. Patients with classic A-T > 12 years also had higher blood (serum/plasma) NfL concentrations (here: compared to age-dependent reference values found in the literature). Patients with classic A-T had higher blood (serum/plasma) NfL concentrations than patients with the variant phenotype. CONCLUSION: Blood (serum/plasma) NfL concentrations are elevated in patients with classic A-T and appear to correlate with the disease phenotype (classic versus variant). Therefore, blood (serum/plasma) NfL may be a promising biomarker in A-T.

Overexpression of Superoxide Dismutase Protects Plants from Oxidative Stress (Induction of Ascorbate Peroxidase in Superoxide Dismutase-Overexpressing Plants).

Photosynthesis of leaf discs from transgenic tobacco plants (Nicotiana tabacum) that express a chimeric gene that encodes chloroplast-localized Cu/Zn superoxide dismutase (SOD+) was protected from oxidative stress caused by exposure to high light intensity and low temperature. Under the same conditions, leaf discs of plants that did not express the pea SOD isoform (SOD-) had substantially lower photosynthetic rates. Young plants of both genotypes were more sensitive to oxidative stress than mature plants, but SOD+ plants retained higher photosynthetic rates than SOD- plants at all developmental stages tested. Not surprisingly, SOD+ plants had approximately 3-fold higher SOD specific activity than SOD- plants. However, SOD+ plants also exhibited a 3- to 4-fold increase in ascorbate peroxidase (APX) specific activity and had a corresponding increase in levels of APX mRNA. Dehydroascorbate reductase and glutathione reductase specific activities were the same in both SOD+ and SOD- plants. These results indicate that transgenic tobacco plants that overexpress pea Cu/Zn SOD II can compensate for the increased levels of SOD with increased expression of the H2O2-scavenging enzyme APX. Therefore, the enhancement of the active oxygen-scavenging system that leads to increased oxidative stress protection in SOD+ plants could result not only from increased SOD levels but from the combined increases in SOD and APX activity.

Possible role of collagen in transverse myelitis and chymopapain-induced paraplegia.

We studied the effect of nucleus pulposus (NP) on platelet aggregation. Our in vitro experiments showed that NP extract produced platelet aggregation and the addition of collagenase to the NP extract abolished this response. It was further shown that chymopapain did not affect the activity of the extract. We assume that collagen is the active platelet aggregant in the NP extract. Intravascular release of collagen may cause platelet aggregation, vascular obstruction, ischemia, and cord necrosis in a patient with acute transverse myelitis. Intradiskal chymopapain is known to cause transverse myelitis and it is possible that collagen released during the action of the enzyme initiates a similar chain of events.

Structural changes in the human vas deferens after tantalum clip occlusion and conventional vasectomy.

In 15 human subjects, the vasa deferentia were occluded by applying two tantalum clips on one side and by conventional vasectomy with silk ligatures on the other. After 2 weeks, the occluded segments were recovered for histopathologic examination of serial sections. Obstructing the seminal tract did not, as such, produce any significant change in the vas: the distal and proximal segments appeared to be essentially similar and normal. At the actual site of occlusion, however, tantalum clips produced marked flattening of the tube, complete loss of lining epithelium, distortion of the muscular lamellae, and areas of hemorrhage. The lumen was converted into a narrow slit. Under the ligatures, the damage was largely confined to denudation of the mucosal epithelium. The mucosa of the intersegment left unexcised between two clips showed hyalinization, invasion by macrophages, and degeneration of the epithelium. The changes under the clips suggest that, although clip occlusion may offer several advantages, sterility cannot be reversed merely by removing the clips. The mechanisms of these changes, different in the case of clips and ligatures, are discussed and some possible long-term consequences are considered.

Vas occlusion by tantalum clips and its comparison with conventional vasectomy in man: reliability, reversibility, and complications.

Occlusion of the vas deferens has been carried out by applying tantalum clips in 60 men. Another 50 men were vasectomized conventionally and served as controls. Vasography showed that two clips were required on each vas to bring about perfect and firm occlusion. The incidence of postoperative infection and other complications was much lower in the clip-occluded cases. Under a long-term follow-up, 10% of the conventionally vasectomized men were dissatisfied with the operation as compared with 2% of the clip-occluded group. Both groups became azoospermic within 3 months and the failure rate was zero. Removal of the clips not only was difficult but left the vas compressed and leaking. The method cannot, therefore, be considered reversible by itself. However, recanalization could easily be achieved by end-to-end anastomosis after excision of the small clipped segment or by side-to-side anastomosis without any excision. This, damage to the neuromuscular apparatus of the vas may be minimized. Male sterilization by clip occlusion has the advantages of minimal surgical intervention, shorter operative time, safety from postoperative infection, and easier recanalization if desired.

Cs frequency synthesis: a new approach.

The paper describes a new approach to synthesizing the Cs hyperfine frequency of 9.192 GHz that is designed to be sufficiently rugged for use in space, specifically for the Primary Atomic Reference Clock in Space (PARCS) planned for the International Space Station, as well as ground applications. This new approach requires no narrow band filters or frequency multiplication, and the primary source of cooling is conduction. Instead of frequency multiplication, it uses a custom regenerative divider stage followed by two commercial binary dividers and several mixing stages. A fractional frequency step of 2x10(-17) is achieved by mixing the output of a 48-bit numerically controlled oscillator with the microwave signal. Preliminary tests on the new synthesizer design indicate an internal fractional frequency stability of 1x10(-15) at 10 s and 1x10 (-18) at 1 d, dominated by the daily room temperature variations. The phase and amplitude noise are similar to our previous designs that used frequency multiplication and narrow band filters. The temperature coefficient is less than 0.2 ps/K.

Tubercular mastitis.

Tuberculosis, a relatively rare lesion in the breast, was observed in 18 patients (seventeen of whom were of child bearing age) with an incidence of 1.02%. Coincidental tuberculosis of the faucial tonsils of suckling infants is suggested as the most common route of infection, especially in the primary type of tubercular mastitis. Conservative surgery under antitubercular therapy cover was found most appropriate.

A correlative study of seminal biochemistry and testicular histology in infertile males.

Two androgen-dependent constituents of the seminal plasma, fructose and acid phosphatase, have been estimated in 50 infertile males along with a testicular biopsy. Azoospermics, as a group, showed a very wide range of fructose (16-600 mg%) as compared to 210-397 mg% in healthy fertile males. Oligospermics tended to have low values with a mean of 218 +/- 75.1 mg%. Acid phosphatase in the controls was 1927 +/- 164.6 K.A. unit/ml and was generally higher in the infertile groups. The state of spermatogenesis, as revealed by testicular biopsy, bore no consistent relationship with the seminal fructose or acid phosphatase. It appears that there may be no inter-relationship between the activity of the germinal epithelium and the secretion of the accessory glands and, although both are androgen-dependent, they can be affected separately by a multitude of factors in human infertility.

Development and use of chlorotetracycline fluorescence as a measurement assay of chloroplast envelope-bound mg.

Experiments were conducted to develop chlorotetracycline (CTC) fluorescence as an assay of Mg(2+) bound to the envelope of the intact chloroplast. This assay technique has been widely used to measure envelope associated divalent cations in animal cell and subcellular systems, but has not been used with chloroplasts. Chloroplast envelope-associated Mg(2+) was altered by pretreatment with Mg(2+) and divalent cation chelating agents and by additions of Mg(2+) to the CTC assay medium. Results indicated that for a given chloroplast preparation, relative changes in envelope-associated Mg(2+) can be effectively monitored with CTC fluorescence. It was concluded that the limitations of this assay system are: (a) chlorophyll strongly quenches CTC fluorescence signal, so a constant chlorophyll concentration must be maintained, (b) measurements must be made quickly, and (c) use of the technique to compare different chloroplast preparations may not be valid. Studies with (28)Mg(2+) confirmed our interpretation of the fluorescence results, and also suggested that the chloroplast envelope is fairly impermeable to Mg(2+). It was concluded that changes in Mg(2+) associated with the chloroplast due to incubation of plastids in solutions containing up to 5 millimolar Mg(2+) may be exclusively due to increased envelope-associated Mg(2+). The CTC assay was used in experiments to demonstrate that increases in chloroplast envelope-associated Mg(2+) inhibit photosynthetic capacity. This inhibition can be partially overcome by the presence of K(+) in the photosynthetic reaction media.

Osmotic adjustment, symplast volume, and nonstomatally mediated water stress inhibition of photosynthesis in wheat.

At low water potential (psi(w)), dehydration reduces the symplast volume of leaf tissue. The effect of this reduction on photosynthetic capacity was investigated. The influence of osmotic adjustment on this relationship was also examined. To examine these relationships, comparative studies were undertaken on two wheat cultivars, one that osmotically adjusts in response to water deficits (;Condor'), and one that lacks this capacity (;Capelle Desprez'). During a 9-day stress cycle, when water was withheld from plants grown in a growth chamber, the relative water content of leaves declined by 30% in both cultivars. Leaf osmotic potential (psi(s)) declined to a greater degree in Condor plants. Measuring psi(s) at full turgor indicated that osmotic adjustment occurred in stressed Condor, but not in Capelle plants. Two methods were used to examine the degree of symplast (i.e. protoplast) volume reduction in tissue rapidly equilibrated to increasingly low psi(w). Both techniques gave similar results. With well-watered plants, symplast volume reduction from the maximum (found at high psi(w) for each cultivar) was the same for Condor and Capelle. After a stress cycle, volume was maintained to a greater degree at low psi(w) in Condor leaf tissue than in Capelle. Nonstomatally controlled photosynthesis was inhibited to the same degree at low psi(w) in leaf tissue prepared from well-watered Condor and Capelle plants. However, photosynthetic capacity was maintained to a greater degree at low psi(w) in tissue prepared from stressed Condor plants than in tissue from stressed Capelle plants. Net CO(2) uptake in attached leaves was monitored using an infrared gas analyzer. These studies indicated that in water stressed plants, photosynthesis was 106.5% higher in Condor than Capelle at ambient [CO(2)] and 21.8% higher at elevated external [CO(2)]. The results presented in this report were interpreted as consistent with the hypothesis that there is a causal association between protoplast (and presumably chloroplast) volume reduction at low psi(w) and low psi(w) inhibition of photosynthesis. Also, the data indicate that osmotic adjustment allows for maintenance of relatively greater volume at low psi(w), thus reducing low psi(w) inhibition of chloroplast photosynthetic potential.

Chloroplast osmotic adjustment and water stress effects on photosynthesis.

Previous studies have suggested that chloroplast stromal volume reduction may mediate the inhibition of photosynthesis under water stress. In this study, the effects of spinach (Spinacia oleracea, var ;Winter Bloomsdale') plant water deficits on chloroplast photosynthetic capacity, solute concentrations in chloroplasts, and chloroplast volume were studied. In situ (gas exchange) and in vitro measurements indicated that chloroplast photosynthetic capacity was maintained during initial leaf water potential (Psi(w)) and relative water content (RWC) decline. During the latter part of the stress period, photosynthesis dropped precipitously. Chloroplast stromal volume apparently remained constant during the initial period of decline in RWC, but as leaf Psi(w) reached -1.2 megapascals, stromal volume began to decline. The apparent maintenance of stromal volume over the initial RWC decline during a stress cycle suggested that chloroplasts are capable of osmotic adjustment in response to leaf water deficits. This hypothesis was confirmed by measuring chloroplast solute levels, which increased during stress. The results of these experiments suggest that stromal volume reduction in situ may be associated with loss of photosynthetic capacity and that one mechanism of photosynthetic acclimation to low Psi(w) may involve stromal volume maintenance.

Response of photosynthesis and cellular antioxidants to ozone in populus leaves.

Atmospheric ozone causes formation of various highly reactive intermediates (e.g. peroxyl and superoxide radicals, H(2)O(2), etc.) in plant tissues. A plant's productivity in environments with ozone may be related to its ability to scavenge the free radicals formed. The effects of ozone on photosynthesis and some free radical scavengers were measured in the fifth emergent leaf of poplars. Clonal poplars (Populus deltoides x Populus cv caudina) were fumigated with 180 parts per billion ozone for 3 hours. Photosynthesis was measured before, during, and after fumigation. During the first 90 minutes of ozone exposure, photosynthetic rates were unaffected but glutathione levels and superoxide dismutase activity increased. After 90 minutes of ozone exposure, photosynthetic rates began to decline while glutathione and superoxide dismutase continued to increase. Total glutathione (reduced plus oxidized) increased in fumigated leaves throughout the exposure period. The ratio of GSH/GSSG also decreased from 12.8 to 1.2 in ozone exposed trees. Superoxide dismutase levels increased twofold in fumigated plants. After 4 hours of ozone exposure, the photosynthetic rate was approximately half that of controls while glutathione levels and superoxide dismutase activity remained above that of the controls. The elevated antioxidant levels were maintained 21 hours after ozone exposure while photosynthetic rates recovered to about 75% of that of controls. Electron transport and NADPH levels remained unaffected by the treatment. Hence, elevated antioxidant metabolism may protect the photosynthetic apparatus during exposure to ozone.