Immunolocalization of duodenal cytochrome B: a relationship with circulating markers of iron status

BACKGROUND

The brush border ferric reductase (Dcytb) is critical for the absorption of dietary iron and appears to be expressed on the duodenal enterocyte brush border. The Dcytb expression is increased in severe iron-deficient anaemia, but the situation in a more typical mild iron deficiency is unclear. This study investigated Dcytb expression in patients with normal iron status or mild iron deficiency and its relationships with enterocyte iron status.

MATERIALS AND METHODS

Duodenal biopsy specimens and blood samples were obtained from 32 patients undergoing routine upper gastrointestinal endoscopy. Twenty-three specimens (six iron-deficient and 17 iron-replete) were processed for light-microscopy (LM) and for immunohistochemistry with antibodies against Dcytb and heavy/light chain ferritin subunits. The nine remaining biopsies (three iron-deficient and six iron-replete) were processed for electron microscopy (EM). Immunolocalization of Dcytb and intracellular ferritin was performed with appropriate primary antibodies followed by 10-nm gold conjugate labels.

RESULTS

The LM process showed a strong negative correlation between immunolabelling intensity of Dcytb on the enterocyte brush border and serum iron saturation (P < 0.001), but only a weak negative correlation between this antigen and haemoglobin (P = 0.08) or serum ferritin concentrations (P = 0.4). EM confirmed anti-Dcytb preferential labelling of microvilli rather than enterocyte cytoplasm (P = 0.001), but preferential antiferritin labelling of cytoplasm (P < 0.02). There was no correlation with enterocyte cytoplasmic ferritin labelling (i.e. enterocyte iron status and Dcytb expression).

CONCLUSIONS

Enterocyte Dcytb brush border expression is increased even in mild iron deficiency and may be related to serum iron saturation. The lack of correlation with enterocyte ferritin expression deserves further study with direct measurement of intracellular iron.

Electron beam damage studies of synthetic 6-line ferrihydrite and ferritin molecule cores within a human liver biopsy

In order to achieve an accurate understanding of the crystal structure of 6-line ferrihydrite (6LFh) and ferritin molecule cores within a human liver biopsy using transmission electron microscopy (TEM), electron beam damage should be considered. For the case of 6LFh, the electron energy loss near-edge structure (ELNES) of core ionisation edges in the electron energy loss spectrum (EELS) combined with multiple linear least-square (MLLS) fitting of reference spectra together with analysis of selected area electron diffraction (SAED) patterns suggests that the iron in 6LFh is solely octahedrally coordinated Fe3+. With increasing electron dose, an increasing percentage of this octahedrally coordinated Fe3+ migrates to tetrahedral sites. When the dose exceeds 3 x 10(8) electrons/nm2, Fe2+ is found to be present in the material. This method also indicates that the iron in ferritin molecule cores within a human liver biopsy is the same as in 6LFh, entirely Fe3+ in octahedral coordination with oxygen. Again the percentage of octahedrally coordinated Fe3+ decreases as the accumulated electron dose increases and Fe2+ is produced in the liver biopsies when the electron dose exceeds 10(6)electrons/nm2.

Changes in intracellular electrolyte concentrations during apoptosis induced by UV irradiation of human myeloblastic cells

Decreases in the intracellular concentrations of both K+and Cl−have been implicated in playing a major role in the progression of apoptosis, but little is known about the temporal relationship between decreases in electrolyte concentration and the key events in apoptosis, and there is no information about how such decreases affect different intracellular compartments. Electron probe X-ray microanalysis was used to determine changes in element concentrations (Na, P, Cl, and K) in nucleus, cytoplasm, and mitochondria in U937 cells undergoing UV-induced apoptosis. In all compartments, the initial stages of apoptosis were characterized by decreases in [K] and [Cl]. The largest decreases in these elements were in the mitochondria and occurred before the release of cytochrome c. Initial decreases in [K] and [Cl] also preceded apoptotic changes in the nucleus. In the later stages of apoptosis, the [K] continued to decrease, whereas that of Cl began to increase toward control levels and was accompanied by an increase in [Na]. In the nucleus, these increases coincided with poly(ADP-ribose) polymerase cleavage, chromatin condensation, and DNA laddering. The cytoplasm was the compartment least affected and the pattern of change of Cl was similar to those in other compartments, but the decrease in [K] was not significant until after active caspase-3 was detected. Our results support the concept that normotonic cell shrinkage occurs early in apoptosis, and demonstrate that changes in the intracellular concentrations of K and Cl precede apoptotic changes in the cell compartments studied.

Biphasic behavior of changes in elemental composition during staurosporine-induced apoptosis

Although the identification of events that occur during apoptosis is a fundamental goal of apoptotic cell death research, little is know about the precise sequence of changes in total elemental composition during apoptosis. We evaluated total elemental composition (Na, Mg, P, Cl, S, and K) in relation to molecular and morphological features in human U937 cells induced to undergo apoptosis with staurosporine, an intrinsic pathway activator. To evaluate total elemental content we used electron probe X-ray microanalysis to measure simultaneously all elements from single, individual cells. We observed two phases in the changes in elemental composition (mainly Na, Cl and K). The early phase was characterized by a decrease in intracellular K (P<0.001) and Cl (P<0.001) content concomitant with cell shrinkage, and preceded the increase in proteolytic activity associated with the activation of caspase-3. The later phase started with caspase-3 activation, and was characterized by a decrease in the K/Na ratio (P<0.001) as a consequence of a significant decrease in K and increase in Na content. The inversion of intracellular K and Na content was related with the inhibition of Na+/K+ ATPase. This later phase was also characterized by a significant increase (P<0.001) in intracellular Cl with respect to the early phase. In addition, we found a decrease in S content and an increase in the P/S ratio. These distinctive changes coincided with chromatin condensation and DNA fragmentation. Together, these findings support the concept that changes in total elemental composition take place in two phases related with molecular and morphological features during staurosporine-induced apoptosis.

Tuberculosis and HIV seroprevalence in Lambeth, Southwark and Lewisham, an area of South London

Since the mid-1980s the number of cases of TB notified within the U.K. has continued to rise although the contribution of HIV to this rise remains unclear. A 12-month prospective cohort study was conducted at chest and HIV clinics in four hospitals in Lambeth, Southwark and Lewisham (LSL), an area of South London, to determine the proportion of patients with culture-proven TB infected with HIV. Secondary aims were to determine the proportion of patients with TB and undiagnosed HIV at first presentation to chest clinics, to determine the proportion of patients presenting with TB as an AIDS defining illness (ADI) and to identify risk factors for co-infection with TB and HIV. In chest clinics, demographic data and left-over blood from patients aged 16 or over with culture-proven TB was collected, anonymised and HIV tested. In HIV clinics, demographic data on patients with TB already known to be HIV seropositive were also obtained. Twenty-one patients (13%, 95% CI-8-19%) of 159 with culture-proven TB were infected with HIV Four (3%) of 133 patients at first presentation to chest clinics had undiagnosed HIV; two were subsequently diagnosed. Of the 21 patients withTB and HIV, nine (43%) presented with TB as an ADI. Patients with TB and HIV were significantly more likely to be aged between 35 and 55 years compared to HIV seronegative patients [12/21 (57%) vs. 38/138 (28%), P=0.006]. None of the patients from the Indian Subcontinent were HIV seropositive [0/21 vs. 25/138 (18%), P=0.047]. At the present time, universal HIV testing of patients with culture-provenTB in chest clinics within the U.K. is unlikely to significantly reduce the number of patients with undiagnosed HIV.

Potassium concentration is reduced in cultured rabbit tracheal smooth muscle cells after withdrawal of serum

Comparison of elemental concentrations in growth-arrested airway smooth muscle cells with those in their proliferating counterpart showed that potassium (K(+)) was significantly reduced, whereas concentrations of other elements sodium (Na(+)), magnesium (Mg(2+)), phosphorus (P), and chlorine (Cl(-)) remained unchanged. Reduced K(+)concentration was associated with a change in the cells from a spindle shape to a flattened form.

Long freeze-drying times are not necessary during the preparation of thin sections for X-ray microanalysis

The temperature profile that occurs when a brass block warms up in a vacuum evaporation unit was determined. Freshly drawn human blood was concentrated by centrifugation, and the pellet was cryofixed and cryosectioned. The cryosections were subject to different freeze-drying protocols, using a freeze-drier with a temperature-controlled stage, to determine the effect of freeze-drying time on element distribution. Spectra were collected by spot analyses at various distances across the interface between red cells and plasma. Concentrations of sodium were high and variable outside the cell and low in the cell interior, with potassium showing the reverse distribution. The number of counts under the iron peak closely followed the potassium distribution. The concentration of sodium was higher than expected at 40 nm inside the cell membrane. This was attributed to the formation of ice crystals at the interface between the cells and plasma during cryofixation and the use of a wide probe size.

Changes in elemental content during apoptotic cell death studied by electron probe X-ray microanalysis

Recent data suggest that changes in ionic content, primarily potassium, play a pivotal role in the progression of apoptosis. However, the changes in total element content, i.e., sodium (Na), magnesium (Mg), phosphorous (P), chlorine (Cl), potassium (K), and calcium (Ca), during apoptosis have not been evaluated. Electron probe X-ray microanalysis (EPXMA) was used to measure total element content in U937 cells before and after the induction of apoptosis. As an experimental model we used U937 cells irradiated with ultraviolet (UV) light. Apoptosis was evaluated with phase-contrast microscopy, with scanning and transmission electron microscopy, and with the fluorescent dye bisbenzimide (Hoechst 33342). Plasma membrane permeability as a measure of cell death was determined by trypan blue dye exclusion. To investigate element content with EPXMA, cells were cryoprepared, i.e., cryofixed and freeze-dried, and analyzed as whole cells using a scanning electron microscope. We found that the UV irradiation induced rapid (within 2 h) morphological changes associated with apoptosis, such as plasma membrane blebbing, condensation of the chromatin, and the formation of membrane-bound apoptotic bodies. At this time, 95% of the apoptotic cells excluded trypan blue dye. EPXMA results demonstrated that UV light-irradiated apoptotic cells (cells with membrane-bound apoptotic bodies) had a lower Cl content (P < 0.001) and K content (P < 0.001) and a higher Na content (P < 0.001) in comparison with nonirradiated control cells. Also, P and Ca content was higher in apoptotic cells than in control cells, but this difference did not reach statistical significance. No differences were found in Mg. These data indicated that morphological changes characteristic of apoptotic cell death are related with significant changes in sodium, chlorine, and potassium content. In addition, we demonstrated that these changes in elemental composition were not associated with loss of cell membrane integrity.

A procedure to prepare cultured cells in suspension for electron probe X-ray microanalysis: application to scanning and transmission electron microscopy

We describe a simple procedure to prepare cultured cells in suspension to analyse elemental content at the cellular level by electron probe X-ray microanalysis. Cells cultured in suspension were deposited onto polycarbonate tissue, culture plate well inserts, centrifuged at low g, washed to remove the extracellular medium, cryofixed and freeze-dried, and analysed in the scanning mode of a scanning electron microscope. We tested the effect of different washing solutions (150 mM ammonium acetate, 300 mM sucrose, and distilled water) on the elemental content of cultured cells in suspension. The results demonstrated that distilled water was the best washing solution to prepare cultured cells. In addition, the low Na content, high K content and high K/Na ratio of the cells indicated that this procedure, based on the centrifugation at low g followed by cryopreparation, constitutes a satisfactory method to prepare cultured cells in suspension. We also investigated the effects of different accelerating voltages on X-ray signal collection. The results showed that moderate accelerating voltages, i.e. 10-11 kV, should be used to analyse whole cells in the scanning mode of the scanning electron microscope. We show that this method of preparation makes it possible to prepare cryosections of the cultured cells, thus permitting analysis of the elemental content at the subcellular level, i.e. nucleus, cytoplasm and mitochondria, using a scanning transmission electron microscope.

Changes in elemental concentrations are associated with early stages of apoptosis in human monocyte-macrophages exposed to oxidized low-density lipoprotein: an X-ray microanalytical study

This study examines ion homeostasis in monocyte-macrophages committed to death by apoptosis. X-ray microanalysis has been used to demonstrate that intracellular concentrations of potassium decreased whilst those of sodium increased following 3 h of exposure to 100 microg/ml of oxidized low-density lipoprotein (LDL) in vitro. In contrast, the maximal incidence of cell death, as determined by the inability to exclude trypan blue, was not seen until 24 h of exposure. At 12 h, less than 1 per cent of cells were stained using terminal transferase-mediated DNA nick-end labelling, which is generally accepted as a marker of late stages in the apoptotic pathway. This is the first demonstration of early perturbations of ion homeostasis in monocyte-macrophages exposed to concentrations of oxidized LDL known to cause apoptosis.

A cryoclamp for the rapid cryofixation of the isolated blood-perfused rabbit cardiac papillary muscle preparation at predefined times during the contraction cycle

There is increasing evidence that the distribution of monovalent cations in cardiac cells may be non-uniform, particularly in the region immediately beneath the sarcolemma, and we have proposed that a build-up of sodium in this region could be an important factor in the development of ischaemia-reperfusion injury. Electron probe X-ray microanalysis is ideal for the study of such changes in distribution but the application of the technique to this problem imposes severe requirements on the specimen and on the method for cryofixation. The specimen must be perfused through its vasculature so that it can be made truly ischaemic and be successfully reperfused. It is necessary to be able to cryofix the specimen without disturbance of its blood supply, electrical stimulation or temperature. It is also important to know the time in the contraction cycle when cryofixation occurs. Here we describe the design of an automated cryofixation device which can be used to cryofix a blood perfused papillary muscle preparation at predetermined time points in the contraction cycle. Preliminary data obtained from the analysis of rabbit papillary muscles subjected to varying periods of ischaemia are included as an example of the use of the cryoclamp.

Capillary surface area is reduced and tissue thickness from capillaries to myocytes is increased in the left ventricle of streptozotocin-diabetic rats

The left ventricles of normal and diabetic rats, fixed by vascular perfusion were examined using modern stereological techniques to quantify changes in the morphology accompanying streptozotocin-induced diabetes. The heart weight to body weight ratio increased in diabetic rats whilst left ventricular volume remained unchanged. Papillary muscles from the diabetic animals showed prolonged time to peak tension and relaxation, and altered sensitivity to adrenalin and calcium. The apparent cardiomyopathy observed when body weight loss exceeds heart weight loss in experimental diabetes was accompanied by specific pathological changes in the composition of the left ventricle. In the diabetic animals the volume of extracellular components increased threefold and the volume of capillaries fell. The surface density and total surface area of capillaries was reduced, and oxygen diffusion distance to myocyte mitochondria increased. The volume fraction of myocyte mitochondria was reduced during streptozotocin-induced diabetes.

Preparation of cultured airway smooth muscle for study of intracellular element concentrations by X-ray microanalysis: comparison of whole cells with cryosections

Methods for growing and preparing smooth muscle cells, isolated from rabbit trachealis, for X-ray microanalysis studies are presented. The cells are grown on Pioloform-covered gold grids supported on Thermanox coverslips. This provides a growth-compatible substrate which is easy to handle and is easily incorporated into routine cell culture studies. The cells are analysed as whole mounts after removal of growth medium by washing, followed by cryofixation and freeze drying. The effects of different washing media (0.3 M sucrose, 0.15 M ammonium acetate and distilled water) on cytoplasmic elemental content are discussed. A method for growing the cells as monolayers and mounting the cryofixed monolayers for cryosectioning is also given. Comparison of elemental concentrations in the cytoplasm of distilled-water washed cells with those of the cytoplasm of cryosectioned cells obtained from the same animal showed good agreement between values obtained from the two preparative procedures. These methods are therefore easily applied to the study of changes in intracellular element concentrations which may be important in understanding the mechanisms of proliferation which lead to increased airway smooth muscle mass in persistent severe asthma.

A diet enriched in essential fatty acids protects against the loss of lymphocytes which occurs in rats suffering from streptozotocin-induced diabetes

Blood glucose, circulating lymphocyte numbers, and the percentage of T- and B-lymphocytes were measured in diabetic and non-diabetic rats which had been fed on control diets, or diets which included oil of evening primrose or coconut oil. In diabetic animals fed on the control or coconut oil diet the number of circulating lymphocytes decreased; this was caused by a decrease in both T- and B-lymphocytes. The decreases in lymphocyte numbers was less in the diabetic animals fed on the diet enriched in evening primrose oil. In these animals the decrease in T-lymphocytes was less and the percentage of B-lymphocytes was increased. It is suggested that the diet enriched in evening primrose oil exerts its protective effect by providing gamma-linolenic acid which is necessary for biosynthesis of prostaglandin E1.

The effects of dietary potassium depletion on the ultrastructure of cardiac ventricular myocytes in rabbits: a morphometric study

The ultrastructure of cardiac ventricular myocytes isolated from normal and chronically K-depleted rabbits was analysed using morphometric techniques. Myocytes from normal animals showed a quantitatively similar distribution of organelle volumes to those previously reported for isolated myocytes from rat, and for whole myocardium in a variety of species. Myocytes from animals that had been fed a K-deficient diet for 25 days had a significantly increased surface density of junctional sarcoplasmic reticulum with the T-tubules and a significant increase in the surface density of the T-system itself. There were no other differences. The increase in junctional SR and T-system may be related to the defect in cardiac contractility that has been reported for rabbit following K depletion, and may represent an adaptive mechanism acting to protect the heart against Ca overload.

Changes in sodium concentration in cardiac myocytes from diabetic rats

The effects of streptozotocin induced diabetes on rats were studied. The animals showed an increase in blood glucose concentration and a loss of weight from both the body and the heart. Loss of weight from the heart was less severe leading to an increased heart to body weight ratio. Study of element concentrations by X-ray microanalysis showed that there was an increase in intracellular Na concentration in cardiac myocytes from the diabetic animals, but no change in Mg. These results agree with studies which show changes in Na/K ATPase after the onset of diabetes.

Subcellular elemental composition in isolated cardiac myocytes from rabbit following chronic potassium depletion and acute repletion, studied by X-ray microanalysis

X-ray microanalysis was used to estimate K, Na, Cl, Mg, P and S within the mitochondria and the myofibrillar regions of cardiac myocytes from rabbits, following dietary potassium depletion. K depletion caused no changes in mitochondrial K, but myofibrillar K was reduced. There were no changes in Na, Mg or Cl. Both areas showed increases in P but decreases in S. Acute K repletion resulted in a significant overshoot of K in both areas, coupled with a profound decrease in Cl. P was reduced in the mitochondria alone. These results may be partly explained by adaptive changes in Na+ pump activity.

From HeLa cell division to infectious diarrhoea

Hela S3 cells were grown in suspension both randomly and, synchronously using hydroxyurea which blocks cells at the G1/S interface. Cryosections were prepared, freeze-dried and analyzed by X-ray microanalysis. As cells moved into S and through M phases [Na] and [Cl] increased; both returned to normal levels upon re-entering G1 phase. The Na/K ratio was 1:1 in G1 phase. Infection of HeLa S3 cells in G1 phase with vaccinia virus resulted in no change in intracellular [Na]. Infection of neonatal mice with murine rotavirus was localized to villus tip enterocytes and gave rise to diarrhoea which was maximal at 72h post-infection (p.i.). Diarrhoea was preceded by ischemia of villi (18-42h p.i.) and villus shortening (maximal at 42h p.i.), and was also coincident with a dramatic regrowth of villi. At 48h p.i. a proliferative zone of electron lucent cells was observed in villus base regions. Cryosections of infected gut, taken before, during, and after infection, together with corresponding age-matched controls, were freeze-dried and analysed by X-ray microanalysis. At 48h p.i. electron lucent villus base cells were shown to be more hydrated, and, to contain higher levels of both Na and Cl and lower levels of P, S, K and Mg than corresponding control cells. These studies (we argue) increase confidence in the use of X-ray microanalysis in studying biological systems, provide some insight into the process of cell division, and constitute the basis of a new concept of diarrhoeal secretion.

Standards for the application of X-ray microanalysis to biological specimens

A review on the subject of compounds used as standards for biological X-ray microanalysis is presented. The general approach used for standardization has been to use standards which resemble the specimen closely in composition. Thus, standards based on proteins have been used for analysis of quench-frozen cryosectioned specimens, whereas standards based on embedding resins have been used for resin-embedded material. The properties of, and problems associated with, each type of standard are recognized and have been well documented. The choice and analysis of biological material. Attention is drawn to the fact that the problems associated with any quantification procedure need to be kept in mind when analysis of standards is undertaken.

The steady-state and rebreathing methods compared during morphine administration in humans

1. We examined the quantitative and qualitative differences between the steady-state and rebreathing methods of determining CO2-response curves before and after each of two doses of intravenous morphine (0.07 and 0.14 mg kg-1) in four healthy male humans. 2. During each study session steady-state and rebreathing CO2-response curves were determined as an ordered pair (separated by 15 min). Carbon dioxide-response curves were determined for control, after 0.07 mg kg-1 morphine, and after a total of 0.21 mg kg-1 morphine. Each subject was studied on a second occasion when the order of the CO2-response pairing was reversed. 3. The results are discussed and related to a model that may account for the differences based on the step increase in CO2 at the onset of rebreathing, the rate of rise of CO2 during rebreathing and the time constant for the central chemoreflex. 4. Our empirical conclusion is that morphine causes a parallel right shift of the steady-state CO2-response curve and causes a non-specific decrease in the slope of the rebreathing CO2-response curve. We suggest that the parallel shift of the steady-state CO2-response curve is specific to drugs acting on opioid receptors.

Ventilatory response to an inhaled constant CO2 load and added dead space in healthy men, awake and asleep

Experiments were conducted in ten adult men to determine if rapid-eye-movement sleep (REMS) reduced the ventilatory response to two 'steady-state' respiratory loads compared to slow wave sleep (SWS). A constant addition of 150 (or 200) ml/min pure CO2 to the inspirate (7 subjects) and 230 ml of added dead space (5 subjects) were the two respiratory loads. Inspiratory ventilation was measured by pneumotachygraph for at least five continuous minutes in wakefulness, SWS and REMS. The increase in ventilation to both stimuli was equal in SWS and REMS with no suggestion of an impaired response during the latter: increases in ventilation during CO2 loading being 49 and 51%, SWS and REMS, respectively, and during additional dead space they were 53 and 59%, SWS and REMS, respectively. Following the addition of extra dead space, end tidal PCO2 levels did not rise significantly more during REMS compared to SWS (P greater than 0.5). These findings show that when ventilatory responses to CO2 are considered across the whole of REMS (including periods with and without actual eye-movements) then they do not appear to be blunted compared to SWS.

A comparison of the elemental concentrations in tissue thymocytes from diabetic and non-diabetic rats

The elemental concentrations in thymocytes from control and diabetic rats were studied by use of the techniques of cryofixation and X-ray microanalysis to determine whether any changes occur in the diseased state. Decreases in the concentrations of the elements P and K were found in thymocytes from the subcapsular and cortical regions of the gland in thymus tissue taken 4 days after the onset of diabetes. A decrease in the concentration of Mg was also found in thymocytes from the subcapsular region of the gland. These changes suggest that the metabolism of thymocytes in vivo is altered in the diabetic animals.

Concentrations of elements in dying thymocytes from the thymus gland of diabetic rats

Atrophy of the thymus gland occurs in rats made diabetic by a single injection of the drug streptozotocin. Histological studies show the presence of thymocytes with pyknotic nuclei in thymus tissue taken from diabetic animals. Analysis of the elemental content of the pyknotic cells was carried out on freeze dried frozen sections of thymus tissue using the technique of X-ray microanalysis. There was no loss of elements from cells which had undergone the early morphological changes characteristic of pyknosis and which showed the condensed chromatin of pyknotic nuclei. However as the cells shrank and lost the clear distinction between nucleus and cytoplasm there was a loss of elements, particularly Mg and K from the cells. The changes in distribution of elements in the dying thymocytes suggest a method of cell death which does not involve disruption of the plasma membrane.

X-ray microanalysis of cells in suspension and the application of this technique to the study of the thymus gland

Although X-ray microanalysis has become a well established technique in the study of tissues there are still relatively few papers reporting results from cells in culture. Our early investigations on freshly isolated murine thymocytes reported higher than expected concentrations of Na and Cl in these cells but subsequent studies have shown that these high concentrations are artefactual. Rat thymocytes that have been isolated and incubated for a short time to allow them to recover from the isolation procedure have lower concentrations of Na and Cl. Sections prepared from pellets of cells which have been concentrated by centrifugation in a microhaematocrit centrifuge have concentrations of Na and Cl which are within the range that has been described for thymocytes in tissues. This method of concentration can be applied successfully to the study of white cells from the peripheral blood. In diabetic animals pyknotic cells occur in the thymus. These cells are characterised by low concentrations of K but no rise in the concentration of Na. Study of thymocytes isolated from a diabetic animal also show pyknotic cells low in K confirming these observations.

Diabetes mellitus in the rat: diminution in the number of cells in the thymus and of lymphocytes in the blood

In diabetic rats there is a rapid fall in the weight of the thymus with a great loss in the numbers of thymocytes. In this paper we show that there is also a marked diminution in the number of lymphocytes in the peripheral blood, although the numbers of neutrophils and monocytes are not affected. Since the thymus is thought to be the site in which T-lymphocytes develop, it is suggested that the paucity of lymphocytes in the peripheral circulation reflects the loss of cells from the thymus. The diminution in the number of circulating lymphocytes in diabetes may account for the liability of diabetics to suffer severely from infections.

Concentrations of elements in rat thymocytes measured by X-ray microanalysis

Elemental concentrations of rat thymocytes in vivo were studied by X-ray microanalysis of freeze-dried sections. Cells from different regions, the subcapsular zone, the cortex and the medulla were studied in thymic tissue from a number of animals. Generally thymocytes situated in the medulla had higher concentrations of K compared to those in the subcapsular zone. The concentration of Na in the nucleus was constant in the medulla in all animals but some variation in this element was seen between animals in the subcapsular zone. The distribution of K/Na ratio in individual thymocytes was different in each region of the thymus. Cells with low K/Na ratio (less than 5) were predominant in the subcapsular zone, whereas cells with higher values for K/Na ratio were found in the cortex and medulla. The subcapsular zone is the region where mitotic cells are mostly situated. The finding of thymocytes with higher concentrations of Na and low K/Na ratios in this region is in accord with in vitro studies on thymocyte stimulation.

Elemental concentrations in isolated rat thymocytes prepared for cryofixation in the presence of different media

Rat thymocytes were isolated in suspension and the effect of preparing the cells for cryofixation in the presence of different media on the elemental content was investigated using the technique of X-ray microanalysis. Cells prepared in the different media showed variation in the concentrations of Na, K and Cl. The isolated cells were incubated at 310 K for 1 h to allow recovery from isolation. There was a decrease in Na and Cl content after incubation. The thymocyte population was disturbed by suspension in medium containing dextran, and this resulted in a number of cells with high concentrations of Na and low concentrations of K. These cells did not take up vital dye. Thymocytes were also prepared for freezing by using high-speed centrifugation to concentrate the cells. Thymocytes prepared by this method showed values for concentrations of Na, K and Cl similar to published values for these cells using other methods of estimation. There were, however, consistent differences in Na content between the cells prepared in Hanks' balanced salt solution and those prepared in serum. Factors which affect the apparent concentration of Na and Cl in isolated cells are discussed.

Elemental content of mast cell granules measured by X-ray microanalysis of rat thymic tissue sections

Mast cell granules were examined by fully quantitative X-ray microanalysis of 20 cells in freeze-dried cryosections. The mast cells were situated mainly in the connective tissue of the thymic capsule of five adult male Carworth Sprague Europe rats. In addition 30 red blood cells were analysed from the same sections. Nineteen of the mast cells had granules rich in S and K. One cell had smaller granules, and in this cell the granules contained high [Ca] and [P] instead of high [S] and [K]. In the majority of cells (13) the S:K ratio was highly correlated and less than 2.2, whereas in the remaining six cells the individual granule ratios were very variable in any one cell and much higher. The mean granule [K] (994 +/− 57 mmol kg-1 dry wt) was about four times the mean cytoplasmic level of 227 +/− 81 mmol kg-1 dry wt. The existence of this difference in concentration between the granules and the cytoplasm suggests that the K in the granules must be bound. The relationship between the [K] and [S] is discussed with regard to the possible binding of heparin and amines in the granules.

Application of X-ray microanalysis to cell suspensions of oil palm (Elaeis guineensis Jacq.)

X-ray microanalysis has been used to determine the elemental composition of oil-palm (Elaeis guineesis) cell suspensions without the use of cryoprotectants. Results based on individual cells were gathered over a typical growth cycle of 14 d. During the log phase (5-7 d) there is an increase in the number of cells containing high concentrations of both K (400 mmol kg(-1) dry weight) and P (400 mmol kg(-1) dry weight). Morphologically these cells had thin cell walls and were frequently joined to other cells (two to five cells per clump).

X-ray microanalysis of synchronized HeLa S3 cells infected with Vaccinia virus

X-ray microanalysis has been used to study changes in concentration of P, S, Cl Na and K in synchronized HeLa S3 cells in g1 phase infected with Vaccinia virus. No dramatic redistribution of elements between nucleus and cytoplasm was demonstrated during the first 6 h post-infection, during which time viral shut-off of host protein synthesis occurred. [Cl] increased relative to [Na] and [K] during the first 3 h post-infection. The magnitude and direction of change in [K] and [Na] (from approximately 10 cells/analysis) was compared with data previously obtained by flame photometry (from approximately 10(6) cells/analysis) and found to be remarkably parallel.

X-ray microanalysis of HeLa S3 cells. II. Analysis of elemental levels during the cell cycle

HeLa S3 cells were synchronized using hydroxyurea. Cryoultramicrotomy and X-ray microanalysis were used to study changes occurring in concentrations of elements during the cell cycle of the synchronized cells. Three subcellular compartments were studied: cytoplasm, nucleus and nucleolus. Potassium concentrations showed little fluctuation in all of the cell compartments during the cell cycle. Sodium concentrations increased during S. and M phases, returning to lower levels in the G1 phase. Chlorine concentrations were highest during the S and G2 phases. At all stages of the cell cycle respective concentrations of potassium, sodium, sulphur and chlorine were similar in the cytoplasm and nucleus. Concentrations of phosphorus increased in the nucleus during S, G2 and M, and also showed fluctuations in the nucleolus during the cycle; these were not seen in the cytoplasm. In S, M and M/G1 sodium concentrations were highest in the nucleolus compared with the other compartments. In the cytoplasm these changes resulted in an increase in total monovalent cation concentration (i.e. sodium + potassium) during S, G2 and M, which returned to base levels after mitosis. This increase in monovalent cation concentration is due almost entirely to the increase in sodium, with little change occurring in the concentration of potassium.

X-ray microanalysis of proximal and distal tubule cells in the mouse kidney, and the influence of cadmium on the concentration of natural intracellular elements

Quantitative X-ray microanalysis of frozen freeze-dried sections of mouse cortex have been used to determine the concentrations of Na, Mg, P, S, Cl, K, Ca and Cd in normal mice and those subjected t 0.7 mumol of cadmium chloride in two subcutaneous injections. These injections result in tissue levels of approximately 100 mg Cd/kg dry weight (less than 1 mM) in whole kidney when analysed by atomic absorption spectrometry. There were distinct and characteristic differences — ‘fingerprints’ — in the elemental composition of both cytoplasm and mitochondria in proximal and distal tubules of normal mice that were distributed by the cadmium treatment. The most significant effect of the cadmium injections was a highly significant increase in the sulphur content of the cytoplasm and mitochondria of distal tubules and a loss in concentration of Mg, P, Cl, K, and particularly Na, from the mitochondria. These results are discussed in the light of current concepts of metallothionein induction (metallothionein is a sulphur-rich protein that acts to bind, amongst other metals, cadmium) and the lack of damage observed in the distal tubules.

X-ray microanalysis of HeLa S3 Cells. I. Instrumental calibration and analysis of randomly growing cultures

Cryo-ultramicrotomy and X-ray microanalysis were used to study the elemental composition of HeLa S3 cells. Quantitation was achieved by reference to elemental standards of known concentration made up in 25% gelatin. Analysis of standards showed linear calibration for each of the elements studied: Na, P, S, Cl, K. Standardization was validated by comparing flame-photometric analysis of gelatin containing sodium potassium tartrate with that of X-ray microanalysis. Freeze-dried sections of cells showed good morphology and analysis of whole sections of the cells showed that K/Na varied in individual cells. Low K/Na could not be ascribed to cell damage or to the sequestering of Na in any particular subcompartment of the cells. Treatment with ouabain caused changes in levels of all the elements studied and resulted in a low K/Na ratio in all cells.

Biosynthesis and characterization of intracellular IgDkappa in a case of CLL

A case of chronic lymphocytic leukaemia (CLL) with diffuse intracellular IgDkappa is reported. No serum paraprotein or urinary Bence-Jones protein were detected. No surface immunoglobulin was found on the neoplastic lymphocytes, but the cells had receptors for Fcgamma and the C3 component of complement consistent with other cases of CLL. Biosynthetic studies confirmed that the cells synthesized IgDkappa but there was no evidence for secretion of IgD into the culture medium. The cells did not produce Ig of any other class. The intracellular IgD occurred predominantly as deltakappa units with no covalent links between the chains. These findings are discussed.

Isolation of a Golgi-apparatus-enriched fraction from leukaemic cells

1. A Golgi-apparatus-enriched fraction was isolated from acute leukaemic lymphoblasts of AKR mice by using an homogenate stabilized with 1 mM-glutaraldehyde. 2. The isolated fraction, which was shown morphologically to be enriched in dictyosomes, possessed between 44- and 76-fold increase in specific activity, compared with the tumour homogenate, of UDP-galactose-glycoprotein galactosyltransferase and between 3- and10.5-fold increase in relative specific activity of UDP-N-acetygalactosamine-polypeptide N-acetylgalactosaminyltransferase. 3. Plasma membranes isolated from the leukaemic lymphoblasts also possessed glycoprotein galactosyltransferase activity, though in contrast with Golgi-apparatus-enriched material had no detectable polypeptide N-acetygalactosaminyltransferase. 4. The difficulties associated with maintaining the morphological integrity of the Golgi apparatus in subcellular fractionation are discussed.

Acquired heart disease in Ugandan children

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