Ecophysiology of xerophytic and halophytic vegetation of a coastal alluvial plain in northern Venezuela: IV. Tillandsia flexuosa Sw. and Schomburgkia humboldtiana Reichb., epiphytic CAM plants

A comparison of the performance of two epiphytes with crassulacean acid metabolism (CAM) was made during the rainy season and dry season at the Ciénega el Ostional, Chichiriviche in northern Venezuela. The epiphytic bromeliad, Tillandsia flexuosa has water-retaining tanks and leaf trichomes, and propagates mainly vegetatively to produce large populations in the shrubby island vegetation. The epiphytic orchid, Schomburgkia humboldtiana formed smaller populations, and had large succulent leaves with uniform chlorenchyma and no distinct water-storage parenchyma, unlike T. flexuosa. Both epiphytes were myrmecophilous. Leaf succulence (kg m^-2 ) declined by ∼ 10% in the dry season for both plants. Both epiphytes showed reduced CO₂ uptake during Phase I (dark period) and (dawn-dusk) titratable acidity (ΔH⁺ ) in the dry season. Water-use efficiency (WUE) was higher for S. humboldtiana (16.0 × 10^-3 mol CO² per mol H² O compared with 5.0 × 10 ^-3 for T. flexuosa) although WUE remained constant during rainy and dry season for each species. Sixty to seventy per cent of the dawn dusk titratable acidity was derived internally from respiratory CO₂ (recycling) for both species, and in absolute terms, recycling decreased in the dry season, in contrast to the expected progression under drought stress. Recycling is an important facet of carbon balance for both species in both rainy and dry seasons. Leaf Na⁺ concentration was higher than values quoted for terrestrial salt stressed CAM plants. Fructose and glucose declined in leaf bases of T. flexuosa during the dark period, but not in the more distal regions of the leaf. S. humboldtiana showed a decrease in sucrose at night, and mannitol was also an important constituent of the leaves. Xylem sap tension maxima increased from 0.38 ± 0.09 MPa (rainy season) to only 0.55 ± 0.06 MPa (dry season) for T. flexuosa, these values being much lower than those found for terrestrial shrubs and herbs at the same site, the two epiphytes use CAM in conjunction with differing morphological adaptations to maintain growth throughout the year at the Ciénega el Ostional, but it would seem that T. flexuosa has better physiological characteristics for maintenance of carbon acquisition during the dry season.

Ecophysiology of xerophytic and halophytic vegetation of a coastal alluvial plain in northern Venezuela: V. The Batis maritime-Sesuvium portulacastrum vegetation unit

The perennial halophytes, Batis maritima L., Sesuvium portulacastrum L., and Portulaca rubricaulis H.B.K. which inhabit the extreme environment on parts of the salt plain and at the edges of the vegetation islands of Ciénega el Ostional were examined to determine their strategies for growth and survival in the rainy and dry seasons. All of the three species are leaf-succulents. High leaf-sap osmotic pressures, xylem tensions and Na⁺ and Cl^- levels indicated that S. portulacastrum and B. maritima are salt-accumulating halophytes. Succulence, leaf-sap osmolalities and Na⁺ and Cl^- levels increased in the dry season in B. maritima by a factor of 1.5-2.0 and in S. Portulacastrum by a factor of 1.9-2.7. B. maritima also accumulated sulphate with a two-fold increase of concentrations in the dry season. In S. portulacastrum Na⁺ accumulation much exceeded Cl^- accumulation and oxalate synthesis was found to serve charge balance. In this species the compatible solutes, proline and pinitol, were clearly detectable in both seasons; their levels increased by a factor of about 6 in the dry season. Exchange of water vapour and CO₂ was measured with a portable steady-state porometer. Photosynthesis in B. maritima showed little response to the transition from the rainy to the dry season while S. portulacastrum was severely impaired in the dry season, showing pronounced midday depressions of gas exchange and about 40% inhibition of light-saturated rates of CO₂ uptake. P. rubricaulis shed its leaves in the dry season. According to carbon isotope ratios (δ¹³ C), B. maritima (δ¹³ C =-26.4‰) and S. portulacastrum (δ¹³ C =-25.8 ‰) are C₃ plants while P. rubricaulis (δ¹³ C =-12.3‰) performed C⁴ photosynthesis.

A longitudinal study of thyroid function in pregnancy

We undertook a prospective longitudinal study of thyroid function in 36 pregnant women. There were significant increases in thyroxin-binding globulin, thyrotropin, and triiodothyronine. Albumin, free thyroxin (measured by an analog and a nonanalog method), and the free thyroxin index were significantly decreased. Results for the free thyroxin methods were correlated with each other in each trimester. We could find no evidence for artifacts related to albumin or thyroxin-binding globulin with either method for free thyroxin.

Ecophysiology of xerophytic and halophytic vegetation of a coastal alluvial plain in northern Venezuela: VI. Water relations and gas exchange of mangroves

Seasonal effects on leaf gas exchange and water relations were compared for Avicennia germinans, a true mangrove, and Conocarpus erectus, a mangrove associate, at coastal sites in northern Venezuela. On the Ciénega el Ostional at Chichiriviche, A. germinans was most abundant around lagoons on the seaward side of the vegetation-free alluvial sand plain. C. erectus was the dominant shrub in inland communities, but the two species co-occurred on vegetation islands at the landward edge of the alluvial plain. On the vegetation islands of the Ciénega el Ostional, gas exchange in A. germinans (a species with foliar salt glands) was less severely curtailed in the dry season compared with the rainy season than was gas exchange in C. erectus (a species lacking salt glands). Average rates of photosynthesis at near-saturating light intensities and total diurnal CO₂ uptake were reduced in the dry season to 69 and 61%, respectively, of their values in the rainy for A. germinans, but to 48 and 30%, respectively, of their rainy-season values for C. erectus. Similarly, stomatal conductance and transpirational water loss were more reduced in the dry season for C. erectus than for A. germinans, with the result that C. erectus showed a 3.4-fold increase in water-use efficiency in the dry season compared with the rainy season. The importance of the soil environment in determining plant gas-exchange Patterns was evidenced by large seasonal shifts in dawn xylem tension for the two species (which increased from 1.34 MPa in the rainy season to 5.50 MPa in the dry season for A. germinans, and from 0.40 to 5.78 MPa for C. erectus). These values reflected changes in the soil environment caused by inundation of the upper soil layers by fresh water in the rainy season and a progressive increase in salt concentrations (to almost twice those in sea water) by evaporation from the soil in the dry season. Large changes in xylem tension were observed for both species during individual day-night cycles, reaching a maximum of 2.36 MPa for A. germinans. For C. erectus, the magnitude of these day-night changes was greatly reduced in the dry season, consistent with its very low transpiration rates at this time of year. Leaf-cell osmotic pressures also tended to be higher in A. germinans than C. erectus (attaining a maximum of 8.3 MPa for A. germinans in the dry season), and were related to the more seaward distribution of the true mangrove on the alluvial plain. Whereas leaves of A. germinans did not show any changes in succulence, leaf succulence in C. erectus increased with leafage and was slightly higher in the dry season than the rainy season. The more succulent leaves also had higher cell-sap osmotic pressures and NaCl concentrations. The most succulent leaves of C. erectus were observed for exposed shrubs growing on the shoreline. During the dry season, these shoreline plants showed high rates of gas exchange and low values for dawn xylem tension (0.89 MPa), indicating that they had access to relatively non-saline water from the shallow water table. On individual plants, exposed shoots had more succulent leaves and higher osmotic pressure and NaCl concentrations than sheltered leaves, demonstrating the importance of foliar absorption of salt borne in sea spray for the ionic relations of C. erectus. Thus, although the distribution of C. erectus is centred on brackish-water zones, this species can apparently extend from habitats with permanent access to a shallow water table through to areas where it is seasonally exposed to low soil water potentials and high salt concentrations in the substratum.

A phantom for electrical impedance tomography

A method has been developed for constructing phantoms for electrical impedance tomography (EIT). A mesh of resistors is soldered to pins in a matrix board and forms a physical realisation of a finite element numerical model. To simulate different body tissues, changes in the apparent electrical conductivity and permittivity can be introduced at a particular location within the phantom by shunting the resistors in the mesh with additional resistors and capacitors. The phantom was used to test an EIT system employing phase-sensitive detection to separate the real and imaginary parts of the peripheral electric potentials. From the measurements images of conductivity and permittivity were reconstructed using an algorithm developed recently. The phantom has good mechanical strength and is electrically stable. The design could easily be reproduced and distributed to other centres developing similar EIT systems to enable testing on a common basis.

Effect of glucose loading on concentrations of chromium in plasma and urine of healthy adults

We report here a small study designed to identify the effect of a 75-g oral glucose load on concentrations of chromium in plasma and urine of apparently healthy volunteers. We detected a consistent and significant (P less than 0.01) decline in plasma chromium after glucose administration, the nadir of the chromium response coinciding with the zenith of the glucose concentration.

Effect of glucose loading on concentrations of chromium in plasma and urine of healthy adults

We report here a small study designed to identify the effect of a 75-g oral glucose load on concentrations of chromium in plasma and urine of apparently healthy volunteers. We detected a consistent and significant (P less than 0.01) decline in plasma chromium after glucose administration, the nadir of the chromium response coinciding with the zenith of the glucose concentration.

Applied potential tomography for non-invasive temperature mapping in hyperthermia

In the field of hyperthermia for cancer treatment, much effort is being put into the development of non-invasive temperature monitoring so that the trauma of implanting thermocouple or thermistor probes in the patient can be avoided. Preliminary studies investigating the use of applied potential tomography (APT) for this purpose have been reported. APT has the advantages over other tomographic methods that the instrumentation is inexpensive, transportable, and could easily be accommodated in a hyperthermia treatment environment. Moreover, the temperature coefficient of electrical conductivity is large (2% degrees C-1) compared, for example, with the corresponding quantity in CT, the x-ray attenuation coefficient, which changes by only 0.04% degrees C-1. In our experimental system, 16 electrodes were fixed around a cylindrical block of agar simulating a human thigh. The system was driven with 5 mA at 50 kHz. The agar was heated using the 13.56 MHz capacitive system currently in clinical use in this hospital. By relating data sets recorded at different times during heating to a set recorded before heating, images of the temperature change in the agar with time were computed and are presented. The experiment was then repeated in vivo on the thigh of a volunteer.

The importance of phase measurement in electrical impedance tomography

A method is described for reconstructing images of electrical conductivity and relative permittivity in electrical impedance tomography (applied potential tomography). The method relies on measurement of both the amplitude and the phase of the surface electric potential profile. The principle is demonstrated using a computer model to simulate measurements. The reconstructed images, referenced to homogeneous saline, agree qualitatively with the values of conductivity and permittivity used in the computer model. In addition, by displaying the imaginary part of the logarithm of the complex electrical conductivity, certain tissues, e.g. liver and kidney, are emphasised on the image. When the same parameter is displayed for simulated dual-frequency measurements, in which 150 kHz values are referenced against 100 kHz, liver and pancreas are emphasised. These results suggest the possibility of distinguishing between different types of soft tissue more effectively than if only signal amplitudes are measured. The phase changes in the simulated signals, on which the formation of such images depends, have a mean value of 13.3 degrees for the saline-referenced simulation but only 1.6 degrees for the dual-frequency simulation requiring accurate measurement in practice.

Immunogenic and antigenic epitopes of immunoglobulin--XX. Denaturation of human IgG3 by free radicals

It has previously been demonstrated that exposure of polyclonal IgG to free radicals results in denaturation evidenced by aggregation, auto-fluorescence and destruction of cysteine, proline and aromatic amino acids. In the present study we have used a panel of monoclonal antibodies (McAb) to epitopes expressed on the IgG3 heavy chain to detect changes in antigenicity. When IgG3 was exposed to u.v. irradiation, as a source of free radicals, subclass specific epitopes were rapidly lost whilst other epitopes were unaffected. Prolonged exposure resulted in further denaturation and a progressive loss of expression of further epitopes. The IgG3 subclass specific McAb are specific to epitopes localized to the hinge region of IgG3. Thus, this exposed cysteine and proline rich region is shown to be particularly vulnerable to free radical attack; however, prolonged exposure results in structural alterations throughout the heavy chain.

A dual-frequency applied potential tomography technique: computer simulations

Applied potential tomography has been discussed in relation to both static and dynamic imaging. We have investigated the feasibility of obtaining static images by measuring profiles at two frequencies of drive current to exploit the differing gradients of electrical conductivity with frequency for different tissues. This method has the advantages that no profile for the homogeneous medium is then needed, and the electrodes can be coupled directly to the skin. To demonstrate the principle, computer simulations have been carried out using published electrical parameters for mammalian tissues at frequencies of 100 and 150 kHz. The distribution of complex electric potentials was calculated by the successive over-relaxation method in two dimensions for an abdominal cross-section with 16 electrodes equally spaced around the surface. From the computed electrode potentials, images were reconstructed using a back-projection method (neglecting phase information). Liver and kidney appeared most distinctly on the image because of their comparatively large conductivity gradients. The perturbations in the electrode potential differences between the two frequencies had a mean value of 5%, requiring accurate measurement in a practical system, compared with 150% when the 100 kHz values were related to a simulation of homogeneous saline equal in conductivity to muscle. The perturbations could be increased by widening the separation of the frequencies. Static imaging using a dual-frequency technique appears to be feasible, but a more detailed consideration of the electrical properties of tissues is needed to determine the optimum choice of frequencies.

Serum creatine kinase-BB levels and cerebral cortical creatine kinase activity in senile dementia of the Alzheimer type

A rise in serum creatine kinase-BB (CK-BB) levels has been reported previously in cases of dementia. In the present study the levels of serum CK-BB have been measured in patients clinically assessed to have senile dementia of the Alzheimer's type (SDAT) and in cognitively intact individuals, matched for age, by a specific two-site monoclonal immunoradiometric assay. No significant difference was found between the 2 groups. Total creatine kinase activity in temporal cortex (Brodmann area 21 and 22) was also found to be similar in brains from SDAT or control cases, obtained at autopsy. These results suggest no major change in the permeability of the blood-brain barrier to this enzyme in SDAT patients.

A modified pharmacokinetic model for platinum disposition in ovarian cancer patients receiving cisplatin

We have fitted a first-order multicompartment pharmacokinetic model to plasma platinum concentrations measured in nine ovarian cancer patients who received intravenous infusions of cisplatin for 6 h. The time-course of ultrafilterable plasma platinum was similar in all patients studied, and was fitted by a single compartment within the limits of experimental detection. However, the time-course of protein-bound platinum showed marked differences between patients, the differences being explained by distribution to two peripheral compartments. The wide inter-patient variation observed in protein-bound plasma platinum concentrations supports the view that pharmacokinetic modelling should be carried out separately for each patient, since averaging plasma concentrations would have obscured some individual pharmacokinetic characteristics.

Specific absorption rate and tissue temperature in local hyperthermia

Specific absorption rate (SAR) and tissue temperature were measured for a total of 83 treatments in 33 patients who received local hyperthermia treatment for cancer. The patients were grouped into three categories according to tumor size. Hyperthermia was induced by 13.56 MHz electromagnetic energy applied using capacitive coupling. A method is described for evaluating SAR from the tissue temperature traces at any time in the treatment when a step change is made in applied power. The method is possible only if the temperature traces are free from interference and the total power delivered to the patient is monitored. Mean values of SAR ranged from 4.6 to 89 W kg-1 depending on the treatment site. Satisfactory heating was achieved for superficial tumors, with temperatures greater than 42 degrees C being recorded in 69% of treatments. For axillary nodes only 4% of treatments exceeded 42 degrees C. For cervix tumors an idealized tumor model was used to estimate tumor temperature from the temperature and SAR measured in the adjacent normal tissue. From the model it appears necessary either to raise the systemic temperature to 40 degrees C or to increase the SAR by at least a factor of 4 to obtain a temperature of 42 degrees C in a typical tumor. Measurements of SAR and temperature are essential for feedback control of computer models which, in principle, could provide a complete distribution of temperature during a hyperthermia treatment. Furthermore, measured SAR provides a direct comparison of the power deposition from different treatment machines in a clinical environment. The data presented form a basis for comparison with the clinical use of other heating systems.

Solitary rib lesions

Solitary rib lesions are not uncommon. They are frequently asymptomatic and usually benign. Virtually all of the malignant tumors are associated with an obvious soft tissue mass which merits further investigation. However, should any of the benign appearing lesions either become symptomatic, change appearance or start growing then they too should be biopsied.

Day-night changes in the leaf water relations of epiphytic bromeliads in the rain forests of Trinidad

A study was made of the bulk-leaf water relations of selected species of epiphytic bromeliads growing in their natural habitat in Trinidad (West Indies). Field measurements were made during the rainy season at three forest sites centred on the wetter part of the island. The epiphytic bromeliads were sampled in situ using modified rock-climbing techniques at 4- to 6-h intervals during complete day-nigh cycles. Eleven species were studied that differed in their photosynthetic pathways and habitat preferences.The C₃ species among the epiphytic bromeliads characteristically showed maximum values of xylem tension (measured with the pressure chamber) during the day, whereas the species with crassulacean acid metabolism (CAM) attained maximum values towards the end of the night. In addition, the CAM species showed large nocturnal increases in leaf-cell-sap osmotic pressure and titratable acidity. These nocturnal increases showed mean values of 0.601 MPa and 289 mol H⁺ m^-3, respectively, for four species sampled at an exposed forest clearing (250 m), where CAM species were well represented. At the other two sites, a lowland forest (60 m) and a ridge forest (740 m), CAM bromeliads were found in the forest canopy, but in the lowest strata all the bromeliads were C₃ species. This species distribution was associated with a marked vertical stratification of microlimate, the forest canopy being characterized by much bigger day-night changes in temperature and water-vapour-pressure deficit than the undergrowth. The C₃-CAM intermediateGuzmania monostachia var.monostachia showed significant nocturnal acidification in the forest clearing but not in the understory of the lowland forest.Taken as a whole, the C₃ and CAM bromeliads were very similar in the range of values observed for xylem tension and osmotic pressure, as well as in aspects of their leaf anatomy. However, epidermal trichomes covered a large percentage of the leaf surface area in xeromorphic species (e.g.Tillandsia utriculata), whereas they were poorly developed in shade-tolerant species (e.g.G. lingulata var.lingulata). The absolute values of sylem tension and osmotic pressure were low for all species. Mean minimum xylem tension during the day-night cycles was in the range of 0.18-0.23 MPa and mean maximum in the range 0.41-0.53 MPa; during periods of rain, xylem tension reached a mean minimum of 0.12 MPa. Mean minimum osmotic pressure was in the range 0.449-0.523 MPa. Such between-site and between-species differences as were observed in the water relations of the bromeliads could be related to the microclimatic conditions prevailing in the various epiphytic habitats.

A new radiological technique for the forefoot

Based on a study of 50 subjects seen at the University of Rochester Medical center, a new axial weightbearing radiological technique of the forefoot is described. The technique is simple, inexpensive, and easily reproducible. It has the advantage of not distorting the forefoot, relationships, unlike currently employed techniques. Since it is performed under weightbearing conditions, the results correlate closer to clinical situations. The subjects under this study, which excluded those with neuromuscular or malalignment problems, were found to fall into two categories: the pain-free and callous-free feet group, who have a well defined arch in the forefoot, and the group of subjects with pain and/or callous under the forefoot, who have a depressed arch. There is also a statistical significance between the relative heights of the tibial and fibular sesamoids. A new classification for hallux valgus based on observations of this technique is proposed.

The inhibition by etomidate of the 11 beta-hydroxylation of cortisol

The effect of a sleep-dose of etomidate on the plasma concentrations of cortisol, 11-deoxycortisol and 17 alpha OH-progesterone was investigated in eight patients; two other patients received thiopentone. Blood samples were collected at 0, 15 and 30 min after etomidate or thiopentone when an injection of tetracosactrin was given and a final sample was collected at 60 min. The plasma cortisol response to tetracosactrin was depressed below normal in patients given etomidate, and the 11-deoxycortisol response was very high, ranging from 36.4 to 184.7 nmol/l. The two patients that received thiopentone had a normal response to all steroids. The identity of the plasma 11-deoxycortisol in two patients was confirmed by high-performance liquid chromatographic separation and quantification by both spectrophotometric and radioimmunoassay measurements. These results suggest that a single dose of etomidate inhibits 11 beta-hydroxylation of cortisol.

Tibiotalar tilt--a new slant

Classically tibiotalar tilt (TTT) is associated with four conditions: Fairbanks disease, hemophilia, sickle-cell anemia and juvenile rheumatoid arthritis. We have found it to be present in at least 20 other conditions including other dysplasias, developmental conditions such as fibrous dysplasia and a variety of other acquired disorders including various metabolic diseases and following previous trauma. The pathogenesis is controversial, but the most probable cause is related to stress and the blood supply of the distal tibial epiphysis. The differentiation of TTT from pseudotibiotalar tilt is also discussed.

Is appendicitis familial?

A family history of appendicectomy was sought in two groups of children admitted to Llandough Hospital over sixteen months. The study group consisted of 29 children with histologically confirmed acute appendicitis, while the control group consisted of 29 children admitted for reasons unrelated to abdominal pain. A history of appendicectomy was elicited in first-degree relatives--that is, siblings and parents of 20 of the children in the study group and of four of the controls--a statistically significant difference. The results obtained from this study suggest that a familial predisposition to appendicitis exists.

Dicarboxylic aciduria: the response to fasting

The urine of a child who presented with an episode of a disease resembling Reye's syndrome was found to contain large quantities of the dicarboxylic acids adipic and suberic acids, as well as the glycine conjugate of suberic acid, suberyl glycine. A variety of other dicarboxylic acids, both saturated and unsaturated, were also found in the urine at the time of the attack. It was found that the excretion of these unusual metabolites could be markedly increased by fasting for periods of greater than 10 h. These results indicate that the patient may have a defect in fatty acid oxidation which becomes clinically significant during periods of prolonged fasting.

Secondary hyperparathyroidism in human kidney transplant recipients

76 kidney transplant recipients who were up to 4 years post transplant, were studied to assess the incidence of secondary hyperparathyroidism. All patients had good renal function with a mean serum creatinine of 1.4 mg/100 ml. Secondary hyperparathyroidism, as evidenced by increased serum parathyroid hormone levels, was present in 53 of the 76 patients (66%) and radiologic bone disease in 26 of the 76 patients (34%), while hypercalcemia (serum calcium greater than 11.0 mg/100 ml) occurred in only 6 patients (8.5%). The incidence of secondary hyperparathyroidism decreased slightly with time following transplantation, but the degree of secondary hyperparathyroidism as indicated by the levels of serum parathyroid hormone at various times following renal transplantation was essentially similar. The causes for the persistence of this condition are not totally known, but it was found that its incidence was related to the duration of dialysis prior to transplantation.

Morphology and chemistry of cell walls of Micrococcus radiodurans

Walls of the pigmented strain of Micrococcus radiodurans showed several layers in the electron microscope. These layers include an outermost network structure removed by trypsin, a fragile soft layer containing hexagonally packed subunits, and a rigid layer penetrated by numerous holes. The two inner layers were separated by a process of autolysis, trypsin treatment, and gradient centrifugation. The hexagonally packed layer was less dense, pink in color, and it contained carotenoids, lipid, protein, and polysaccharide. The lipid consisted of odd-numbered as well as even-numbered fatty acids, and the polysaccharide contained rhamnose and mannose, but it did not contain heptose. The "holey" layer was white and was composed of a mucopeptide containing glucosamine, muramic acid, and four main amino acids (glutamic acid, alanine, glycine, and l-ornithine, in the ratios of 1:1.7:1.8:1.2, respectively). This layer also contained phosphorus, glucose, and a trace of meso- and ll-diaminopimelic acid. A white mutant, W(1), of M. radiodurans had no pigment or lipid in its walls, but it contained small amounts of the "hexagonal" layer. The holey layer, constituting the bulk of the wall, was similar in morphology and composition to that layer in the pigmented strain. Lysozyme did not remove the lipoprotein-polysaccharide component from the walls of the pigmented strains, and the hexagonally packed structure was not visibly affected, except for change in a minor structure. Most of the mucopeptide layer was solubilized by lysozyme, but a structureless bag-shaped residue was left. This residue contained phosphorus, carbohydrate, and limited amino acids, but it did not contain muramic acid, glucosamine, or ornithine. Aqueous phenol removed a lipoprotein component from strain R(1), which contained limited fatty acids. It also removed meso- and ll-diaminopimelic acid.