Seasonal mixing and catastrophic degassing in tropical lakes, cameroon, west Africa.

Lethal gas releases from Lakes Nyos and Monoun in Cameroon seem to be more lacustrine than volcanic in origin. Both of these events occurred in August and were only 2 years apart. Data show that the period of deepest mixing and lake turnover also occurs during late summer in this region of tropical Africa. In addition, recent trends of decreases in both air temperatures and effective insolation relative to long-term means suggest that weakening of stratification, coupled with a predictable seasonal interval of reduced stability in August, may be responsible for the timing of these events.

Arctic lakes and streams as gas conduits to the atmosphere: implications for tundra carbon budgets.

Arctic tundra has large amounts of stored carbon and is thought to be a sink for atmospheric carbon dioxide (CO(2)) (0.1 to 0.3 petagram of carbon per year) (1 petagram = 10(15) grams). But this estimate of carbon balance is only for terrestrial ecosystems. Measurements of the partial pressure of CO(2) in 29 aquatic ecosystems across arctic Alaska showed that in most cases (27 of 29) CO(2) was released to the atmosphere. This CO(2) probably originates in terrestrial environments; erosion of particulate carbon plus ground-water transport of dissolved carbon from tundra contribute to the CO(2) flux from surface waters to the atmosphere. If this mechanism is typical of that of other tundra areas, then current estimates of the arctic terrestrial sink for atmospheric CO(2) may be 20 percent too high.

Carbon dioxide supersaturation in the surface waters of lakes.

Data on the partial pressure of carbon dioxide (CO(2)) in the surface waters from a large number of lakes (1835) with a worldwide distribution show that only a small proportion of the 4665 samples analyzed (less than 10 percent) were within +/-20 percent of equilibrium with the atmosphere and that most samples (87 percent) were supersaturated. The mean partial pressure of CO(2) averaged 1036 microatmospheres, about three times the value in the overlying atmosphere, indicating that lakes are sources rather than sinks of atmospheric CO(2). On a global scale, the potential efflux of CO(2) from lakes (about 0.14 x 10(15) grams of carbon per year) is about half as large as riverine transport of organic plus inorganic carbon to the ocean. Lakes are a small but potentially important conduit for carbon from terrestrial sources to the atmospheric sink.

Prevention of allogeneic bone marrow graft rejection by H-2 transgene in donor mice.

Rejection of bone marrow grafts in irradiated mice is mediated by natural killer (NK) cells and is controlled by genes linked to the major histocompatibility complex (MHC). It has, however, not been possible to identify the genes or their products. An MHC class I (Dd) transgene introduced in C57BL donors prevented the rejection of their bone marrow by NK cells in irradiated allogeneic and F1 hybrid mice expressing the Dd gene. Conversely, H-2Dd transgenic C57BL recipients acquired the ability to reject bone marrow from C57BL donors but not from H-2Dd transgenic C57BL donors. These results provide formal evidence that NK cells are part of a system capable of rejecting cells because they lack normal genes of the host type, in contrast to T cells, which recognize cells that contain abnormal or novel sequences of non-host type.

The 1986 lake nyos gas disaster in cameroon, west Africa.

The sudden, catastrophic release of gas from Lake Nyos on 21 August 1986 caused the deaths of at least 1700 people in the northwest area of Cameroon, West Africa. Chemical, isotopic, geologic, and medical evidence support the hypotheses that (i) the bulk of gas released was carbon dioxide that had been stored in the lake's hypolimnion, (ii) the victims exposed to the gas cloud died of carbon dioxide asphyxiation, (iii) the carbon dioxide was derived from magmatic sources, and (iv) there was no significant, direct volcanic activity involved. The limnological nature of the gas release suggests that hazardous lakes may be identified and monitored and that the danger of future incidents can be reduced.

Resident interpretation of emergency computed tomographic scans.

Our busy, urban emergency room is staffed by radiology residents after working hours. To determine the accuracy of our residents' interpretations of emergency cranial computed tomographic (CT) scans, the authors reviewed the preliminary reports of our residents for a two-month period. A total of 289 cranial CT scans were retrospectively reviewed and the resident interpretation judged acceptable, minor error, moderate error, or major error. Six of 289 neurologic examinations (2%) had moderate (4) or major (2) errors. The mistakes all involved misinterpretation of cerebral hemorrhage. The 98% accuracy in interpretation of cranial CT is higher than the accuracy reported with emergency plain film (PF) interpretation.

Surface coil FLASH magnetic resonance imaging of the fasting and secretin-stimulated pancreas.

The purpose of this study is to investigate the response of the pancreas to secretin stimulation using magnetic resonance imaging (MRI). Using the Siemens 1.0 T Magnetom and a Helmholtz surface coil, single breath FLASH-MRI of the normal fasting pancreas was performed in the prone position, both before and after a 20-minute period after intravenous (IV) bolus injection of secretin (2 cu/kg). T2*-weighted fast low-angle shot sequences (TR = 150 mseconds; TE = 30 mseconds; flip angle = 10 degrees; matrix = 256 X 256; acquisitions = 2) demonstrated an immediate response manifested by a significant distension of the duodenum with fluid secreted by the pancreas, as well as a gradual decline of the pancreas/muscle signal intensity (SI) ratio over time. Twenty minutes after secretin administration, the mean percent decrease of the pancreas/muscle SI ratio in six volunteers was 11.6 +/- 6.4 (1-STD). This is statistically significant (P less than .003) given a mean percent increase of the pancreas/muscle SI ratio of 1.6 +/- 4.8 (1-STD) in five volunteers 20 minutes after bolus injection of saline (control). Although significant duodenal distension is easily demonstrated after secretin administration, the decrease of the relative pancreatic SI over time is visually subtle. Further work is needed to enhance imaging of the physiologic response of the pancreas using even more rapid imaging techniques.

Subtyping lymphocytes in peripheral blood by direct immunoalkaline phosphatase labeling and light scatter/absorption flow cytometric analysis.

Evaluation of blood cells to determine immunologic status is becoming an important clinical application of flow cytometric analysis. For a wider use of immunophenotyping technology in clinical laboratories, the authors developed a rapid method to detect monoclonal antibody-labeled cells using forward light scatter/absorption clinical flow cytometers such as the Technicon H*1 and Technicon H*2 differential complete blood count analyzers. Calf-intestinal alkaline phosphatase was conjugated to mouse monoclonal antibodies (anti-CD2, CD3, CD4, CD8, CD19) for direct immunoenzymatic labeling. The combination of 5-bromo-4-chloro-3-indolyl phosphate and nitroblue-tetrazolium salt in diethanolamine buffer at pH 9.6 was selected as buffer/substrate to yield stable, insoluble, and very intense purplish-blue precipitates on the surface of the cells labeled with monoclonal antibody-alkaline phosphatase conjugates. Endogenous alkaline phosphatase in granulocytes was inhibited with levamisole. Early mild fixation of the white cells permitted incubation at 38 +/- 1 degrees C, which accelerated each step of the reaction without disrupting the cells throughout the procedure. The method is competitive with the direct immunofluorescence whole-blood method used on fluorescence flow cytometers in speed, sensitivity, and accuracy, as demonstrated with alkaline phosphatase-conjugated anti-CD2, CD3, CD4, CD8, CD19 monoclonal antibodies.

Cavitation of squamous carcinoma of the lung.

This study indicates that a good percentage of the cavitary squamous cell carcinomas of the lung can be suggested throught the use of sputum cytology. Hyperkeratinized malignant cells associated with varying degrees of karyorrhexis, "ghost cells," and a diathesis of purulent exudate are helpful in the identification of this tumor type. The cell population found cytologically can be demonstrated in the histologic sections of cavitary squamous cell carcinoma of the lung. We readily admit that the application of the above criteria will not decrease the mortality or morbidity of lung cancer, but can be used as a refinement of a diagnostic tool.

Nuclear scintigraphy in the evaluation of renal colic.

Forty patients with acute onset renal colic were studied using technetium-99m DTPA renal scintigraphy. Thirty-two were found to have varying degrees of obstruction. In the obstructed group the level was determined by the scan alone in 24 of 32 cases (75%). When the analysis included an abdominal radiograph, the level of obstruction was ascertained in 29 of 32 cases (91%). A delayed nephrogram, as evidenced by an "empty renal pelvis sign" at 5 minutes, was observed in all but one of the cases of obstruction (97%). Delayed clearance of activity from the pyelocalyceal system or ureter was also seen in 97%. In all cases of obstruction either one or both of these signs were observed. However, delayed clearance was found to be a nonspecific finding and was noted in 25% of nonobstructed cases. The finding of the "empty renal pelvis sign" at 5 minutes was found to be specific and was not seen in the nonobstructed group. The authors conclude that radionuclide renal scanning is an effective method for evaluating selected patients with suspected renal colic.

Histochemical localization of cholinesterases and monoamines in the central heart of Sepia officinalis L. (Cephalopoda).

The central heart of the coleoid cephalopod, Sepia officinalis, was studied using acetylcholinesterase and fluorescence histochemistry. Using histo- and cytochemical reactions, acetylcholinesterase was localized in the axolemma and axoplasm of specific cardiac nerve fibres, as well as in the sarcolemma and within the sarcotubular system of the muscle cells. Butyrylcholinesterase exhibited a different distribution, being found only in the luminal trabecular muscle layer. Glyoxylic-acid-induced fluorescence indicated the presence of catecholamines (emission maximum, 470 nm) in cardiac nerve axons. These histochemical findings support the hypothesis that noradrenaline and/or dopamine and acetylcholine act antagonistically as natural transmitters. Fluorophores indicating the presence of serotonin were not observed. The present results are discussed in the light of previous pharmacological findings.

Effects of biogenic amines and related agonists and antagonists on the isolated heart of the common cuttlefish Sepia officinalis L.

1. Effects of noradrenaline and the related compounds adrenaline, dopamine, octopamine, tyramine, clonidine and isoprenaline were studied in isolated heart preparations from the cuttlefish Sepia officinalis L. 2. All analogues produced a positive inotropic affect, with noradrenaline being the most potent substance. The chronotropic effects of the tested compounds differed widely. 3. The action of substances of the phenylethanolamine group were not antagonized by propranolol but were partly antagonized by phentolamine. 4. Serotonin and its analogues also produced cardio-excitation. These effects were blocked by cyproheptadine but not by methysergide. 5. These results indicate the presence of two different receptors in the Sepia myocardium: one type reacting with noradrenaline most effectively and a second type being stimulated by serotonin.

Pyogenic sacroiliitis in i.v. drug abusers.

We evaluated the sensitivity of imaging studies in six IV drug abusers who had back pain from pyogenic sacroiliitis. Initial radiographs of the sacroiliac joints showed bone destruction in two. A third had slight joint narrowing and sclerosis resembling degenerative disease. Radiographs were considered normal in three. Two of the patients with initially normal radiographs subsequently showed loss of cortices on follow-up studies within 2 weeks. All of the patients had increased activity on scintigrams (five were obtained with technetium-99m methylene diphosphonate; one was with gallium). The findings suggest that scintigraphy is useful in the detection of pyogenic sacroiliitis in IV drug abusers when plain films are normal.

Hemolytic anti-hr" (e) detectable solely by an automated polybrene technique.

An example of a hemolytic anti-hr" (e) detectable solely by an AutoAnalyzer-Polybrene (AAP) system is reported. The antibody was undetectable by routine indirect antiglobulin and enzyme tests, and produced a delayed intravascular hemolytic transfusion reaction. The anti-hr" (e) was no longer AAP detectable five months after the transfusion reaction. This paper points out the potential usefulness of the AAP technique in detecting alloantibodies in cases of transfusion reactions where no antibody specificity can be demonstrated by standard manual techniques.

Objective assessment of swallowing function in head and neck cancer patients.

Swallowing function was evaluated with scintigraphy in 37 patients with head and neck cancer. The patients were examined before and during the course of either surgery, chemotherapy, and/or radiotherapy. A total of 118 scintigraphic studies were performed. Scintigraphic results of bolus flow and aspiration were correlated with clinical findings. Both scintigraphic and clinical studies indicated a worsened swallowing function in 12 patients. These same studies indicated improvement of swallowing in another 13 patients. In 11 patients, both studies revealed either no apparent change or mixed changes in swallowing function after the course of therapy. In only 1 patient was there disagreement between the scintigraphic and clinical assessment of swallowing function. It is our opinion that scintigraphy is a useful method for objective assessment of swallowing function during and after the course of treatment of head and neck cancer patients.

Computed tomography of nephrogenic adenoma of the urinary bladder.

Nephrogenic adenoma of the urinary bladder is a rare benign tumor. It is generally accepted that the tumor represents metaplasia of the urothelium in response to chronic inflammation or injury. Its CT appearance can be similar to that of carcinoma of the bladder.

Molecular analysis of H-2-deficient lymphoma lines. Distinct defects in biosynthesis and association of MHC class I heavy chains and beta 2-microglobulin observed in cells with increased sensitivity to NK cell lysis.

It has previously been reported that MHC class I-deficient RBL-5 and YAC-1 lymphoma sublines show an enhanced NK sensitivity in vitro. In the present study such lymphoma variants were found to have different defects in H-2 biosynthesis such as 1) reduced beta 2-microglobulin and H-2 H chain transcription, 2) block in beta 2-microglobulin translation, and 3) impaired association between beta 2-microglobulin and H-2 H chains. For lines with the latter two defects, the results suggested that a major part of the H chains were arrested before the middle Golgi complex as indicated by their failure to undergo carbohydrate side chain trimming. The data suggest that NK sensitivity can be directly influenced by the membrane expression of MHC class I gene products of tumor targets because three independent molecular defects, all interfering with the cell surface H-2 expression, gave rise to NK-sensitive phenotypes. These variant lines will also be useful tools for studies of H-2 glycoprotein assembly and transport and for Ag presentation to CTL.

Initial experience with percutaneous placement of the PAS port implantable venous access device.

The authors evaluated a new venous access port designed for peripheral venous insertion in the interventional radiology suite. Forty ports were placed in 40 patients in either the brachial, cephalic, or basilic vein under fluoroscopic guidance. These ports have been used for blood transfusion, blood sampling, parenteral nutrition, chemotherapy, and antibiotic therapy. The ports have been in use for 4,241 consecutive patients days. There have been no clinically apparent venous thrombotic complications and only one device-related infection. The cost and risk of complication are less than those for a surgically placed chest wall port, and the cosmetic result is excellent. This port has had excellent patient, nursing, and clinical acceptance.

Lipoma of the myocardium.

A case of myocardial lipoma is presented which was diagnosed by computed tomography (CT). The resultant distortion of the cardiac chambers was well delineated by CT.

Computer assisted tomography in experimentally induced orbital pseudotumor.

Induction of an entity that is comparable to pseudotumor of the orbit in humans has been performed successfully in the rabbit. Injection of a retrobulbar antigen in a previously sensitized rabbit produced a profound inflammatory mass. Proptosis, soft tissue swelling, and an orbital mass effect were grossly visible after a short interval. Computer assisted tomography disclosed dense orbital mass and uveoscleral thickening. Exenteration specimens confirmed as inflammatory cell mass similar to the histology associated with pseudotumor of the human orbit.