Dual pathways for regulation of root branching by nitrate

Root development is extremely sensitive to variations in nutrient supply, but the mechanisms are poorly understood. We have investigated the processes by which nitrate (NO3-), depending on its availability and distribution, can have both positive and negative effects on the development and growth of lateral roots. When Arabidopsis roots were exposed to a locally concentrated supply of NO3- there was no increase in lateral root numbers within the NO3--rich zone, but there was a localized 2-fold increase in the mean rate of lateral root elongation, which was attributable to a corresponding increase in the rate of cell production in the lateral root meristem. Localized applications of other N sources did not stimulate lateral root elongation, consistent with previous evidence that the NO3- ion is acting as a signal rather than a nutrient. The axr4 auxin-resistant mutant was insensitive to the stimulatory effect of NO3-, suggesting an overlap between the NO3- and auxin response pathways. High rates of NO3- supply to the roots had a systemic inhibitory effect on lateral root development that acted specifically at the stage when the laterals had just emerged from the primary root, apparently delaying final activation of the lateral root meristem. A nitrate reductase-deficient mutant showed increased sensitivity to this systemic inhibitory effect, suggesting that tissue NO3- levels may play a role in generating the inhibitory signal. We present a model in which root branching is modulated by opposing signals from the plant's internal N status and the external supply of NO3-.

On being invisible in the mental health system

The author provides a case study of her daughter's sexual abuse as a child and subsequent experiences as a chronically mentally ill client in the mental health system. Information from 17 years of mental health records and anecdotal accounts are used to illustrate the effects of the abuse, her attempts to reach out for help, and the system's failure to respond. There is evidence that a significant subset of psychiatric patients were severely sexually traumatized in childhood. Yet standard interview schedules consistently neglect to ask questions about such abuse, appropriate treatment is seldom available, and clients are often retraumatized by current practices. Psychiatry's historic resistance to addressing abuse as etiology is being challenged today by powerful economic, political, and professional forces leading to the emergence of a new trauma-based paradigm.

GSLII positivity is not confined to oligodendrocytes in adult mammalian CNS

The in vivo binding pattern of the lectin Griffonia simplicifolia II (GSLII) was evaluated in sections of adult cat optic nerve following reports that it is a marker for oligodendrocytes in adult rodent CNS and that it may also be an oligodendroglial lineage marker. Following as closely as possible the immunocytochemical methodology employed in these reports, staining for GSLII was incorporated into sets of consecutive one micron thick sections comprising known cell-type specific reference markers backed up by electron microscopy. With this correlative protocol both lectin positive and lectin negative cells could be reliably identified. The material examined included normal control tissue and tissue containing previously studied demyelinating lesions of various ages in which oligodendrocyte progenitors and precursors have been characterized. GSLII was found to stain not only mature oligodendrocytes in adult cat optic nerve but also activated microglia, macrophages, polymorphonuclear leucocytes and other haematogenous cells. Lectin positivity was not found in oligodendroglial precursors, endothelial cells, astrocytes or ramified microglia. This study emphasises that care needs to be taken before assigning lineage marker status to individual lectins or antibodies.

Mucin mRNA expression in normal and vasomotor inferior turbinates

Mucins are the major glycoprotein component of respiratory tract secretions. Little is known about their expression in the upper respiratory tract. In order to define this expression, in situ hybridization was performed on 19 normal and 4 vasomotor rhinitis (VMR) inferior turbinates to identify mucin mRNA. MUC1, MUC2, MUC4, MUC5AC, MUC5B, and MUC7 were expressed in both the normal and VMR turbinates. MUC4 and MUC5AC were the most highly expressed mucins. MUC1, MUC2, MUC4, and MUC5AC were expressed mainly by the epithelial border, whereas MUC5B and MUC7 were expressed by the submucosal glands. MUC1 and MUC4 exhibited a diffuse expression by multiple cell types along the mucosal border, whereas MUC2 and MUC5AC expression appeared to be limited to a subpopulation of epithelial cells, most likely goblet cells. Although MUC1, MUC4, and MUC5AC showed sporadic submucosal glandular expression, MUC5B and MUC7 appeared to be the predominant submucosal gland mucins in the inferior turbinates. MUC3 and MUC6 expression, which have been found primarily in the gastric mucosa, were not seen in any of the inferior turbinate samples examined. The only difference seen between normal and VMR turbinates was a slight decrease in MUC1 expression in the VMR group. The variety of mucins expressed and the diversity of their expression patterns may have significance in terms of the rheologic and particle clearance properties of nasal secretions. Understanding the expression patterns in normal turbinates will serve as the foundation for further study of these mucins in disease states.

Magnesium flux during and after open heart operations in children

Hypomagnesemia and depletion of the body's magnesium stores is known to be associated with an increased incidence of both cardiac arrhythmias and neurological irritability. In a two-part prospective study we have evaluated whether magnesium deficiency is a significant occurrence in children treated in the intensive care unit after open heart operations, and subsequently have sought to identify how intraoperative metabolic changes were related to the resultant findings. In 41 children studied after operation the plasma magnesium concentration showed a significant decrease from 0.92 mmol/L (10th to 90th centile, 0.71 to 1.15 mmol/L) immediately after operation to 0.77 mmol/L (0.65 to 0.91 mmol/L) on the following morning. The subsequent change in grouped values was not significant but 14 (34.2%) and 7 (17.1%) possessed values of less than 0.7 mmol/L and 0.6 mmol/L, respectively. The occurrence of cardiac arrhythmias was not statistically related to the occurrence of hypomagnesemia. In 21 children perioperative changes in extracellular and tissue magnesium, potassium, and calcium content were measured. It was found that hemodilution with a prime low in magnesium caused a reduction from a median of 0.81 mmol/L to 0.61 mmol/L (p < 0.01). Plasma potassium level, however, was elevated from 3.7 mmol/L to 4.15 mmol/L (p < 0.05) and the ionized calcium content from 1.17 mmol/L (1.07 to 1.25 mmol/L) to 1.49 mmol/L (1.25 to 2.56 mmol/L) (p = 0.0009). The myocardial content of magnesium did not change significantly but skeletal muscle content was depleted from 6.75 mumol/g (2.85 to 8.35 mumol/g) to 5.65 mumol/g (2.45 to 7.2 mumol/g) (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Magnesium flux caused by coronary artery bypass operation: three patterns of deficiency

We undertook a study to evaluate the patterns of magnesium deficiency that may develop during and following coronary artery bypass operation without cardioplegia. In 18 patients intraoperative measurements of plasma magnesium and potassium concentrations and measurements of cardiac and skeletal muscle content of these ions were taken. The changes in plasma concentrations and excretion were evaluated postoperatively. Hemodilution at initiation of cardiopulmonary bypass caused a 17.3% decrease in plasma magnesium concentration (p < 0.01), which persisted until the first postoperative day. By the fifth postoperative day the level was 19.5% greater than the preoperative value. Urinary excretion of magnesium reflected changes in plasma magnesium concentration. Cardiac muscle content of magnesium decreased by 13.3%. Plasma potassium concentration was elevated by hemodilution (p < 0.01), and muscle potassium was not depleted. We conclude that three patterns of magnesium depletion occur: hemodilution, intraoperative cellular depletion, and postoperative cellular depletion. The findings support the need for magnesium supplementation during and after cardiac operation.

Optical neural network with quantum well devices

An optical implementation of a second-order, translation-invariant neural network algorithm is described. The active devices are two arrays of integrated asymmetric Fabry-Perot modulators. The device and the array characteristics are given. The arrays are used, with passive optics, to provide optical input, matrix multiplication, and weighted interconnects in a cascaded optical system. The detailed parameters of the system are discussed, and the operation is assessed in terms of noise tolerance. Translation invariance is confirmed. Finally, the relative merits of the devices and algorithm are considered.

Optical implementation of a second-order translation-invariant network algorithm

Higher-order networks, particularly second-order translation-invariant networks, are introduced, and their suitability for optical implementation is outlined. The algorithm is implemented with a conventional liquid-crystal display, permitting on-line learning and updating of weights. The basic operation of the optical system is demonstrated, and the ability of the system to adapt to system nonuniformities is illustrated. The implementation with an integrated optoelectronic array of asymmetric Fabry-Perot modulators containing a GaAs/AlGaAs multiple-quantum-well active region is described. The principles of operation and operating characteristics of the device array are outlined. The use of the array in an optical system to calculate the autocorrelation matrix necessary for a second-order network is demonstrated.

Reducing arrhythmias associated with central venous catheter insertion or exchange

A recent study demonstrated that the incidence of new arrhythmias occurring during central venous catheter insertion or exchange was 41% atrial and 25% ventricular arrhythmias (12% couplets or greater). Over-insertion of the guidewire, causing direct stimulation to the right side of the heart, has been postulated to be the causative factor. A new technique that allows the operator to control the length of guidewire inserted was developed. With this technique on a population of hospitalized patients, similar to those in the previous study, the incidence of atrial arrhythmias decreased to 32% and the incidence of ventricular arrhythmias to 6% (single premature ventricular contractions only). Although this new technique has limitations, there was a dramatic improvement in the incidence of cardiac arrhythmias. These results indicate a need for modifications in the available equipment to avoid the infrequent but life-threatening complication of malignant arrhythmia.

Mapping of von Hippel-Lindau disease to chromosome 3p confirmed by genetic linkage analysis

Genetic linkage studies were performed in 12 British families with von Hippel-Lindau disease (VHL) using RFLPs at three loci (DNF15S2, THRB, RAF1) on the short arm of chromosome 3. Linkage was detected between the VHL disease locus and RAF1 with a maximum lod score of 3.88 at a recombination fraction of 0.05 (confidence interval 0.003-0.18). Multipoint linkage analysis suggested that the most likely location for the VHL disease locus is telomeric to THRB. These results confirm earlier reports localizing the VHL gene to the short arm of chromosome 3, and provide no evidence for genetic heterogeneity.

Incidence of arrhythmia with central venous catheter insertion and exchange

The risk of complication during the insertion or exchange of central venous catheters has been well documented. The majority of complications involve mechanical problems associated with insertion. Although cardiac arrhythmia has been acknowledged as a possible complication, its incidence has never been quantified. We performed cardiac monitoring on patients during 51 central venous catheter insertions or exchanges to determine the incidence of cardiac arrhythmias during guidewire insertion. Forty-one percent of procedures resulted in atrial arrhythmias and 25% produced some degree of ventricular ectopy, 30% of these were ventricular couplets or greater. Ventricular ectopy was significantly more common in shorter patients (160 +/- 8 vs 168 +/- 11 cm, p less than 0.05) and when the catheter was inserted from the right subclavian position (43% ventricular ectopy vs 10% at the other sites). Other variables such as age, cardiac history, serum potassium, type of procedure, and catheter brand were not significant. It is our conclusion that over-insertion of the wire causes this cardiac stimulation. Despite the absence of morbidity or mortality in this study, this incidence of ventricular ectopy indicates that there is a distinct possibility of a malignant arrhythmia being precipitated by a guidewire. Some modification of the current protocol for these procedures seems indicated.

Microangiopathy in human diabetic neuropathy: relationship between capillary abnormalities and the severity of neuropathy

Clinical, electrophysiological and ultrastructural morphometric observations were made in 5 diabetic non-neuropathic patients, 5 diabetic patients with mild neuropathy and 11 diabetic patients with severe neuropathy. Capillary abnormalities were assessed in simultaneous nerve, muscle and skin biopsies and compared with results from 6 age-matched, non-diabetic control subjects. Nerve capillaries demonstrated markedly greater pathology than skin and muscle capillaries. Endoneurial capillary density was significantly reduced in severely neuropathic diabetic patients (p less than 0.01) when compared with control subjects. Capillary basement membrane (p less than 0.002), endothelial cell (p less than 0.003) and total diffusion barrier (endothelial cell, pericyte, basement membrane) (p less than 0.001) thickness were significantly increased, and oxygen diffusing capacity was significantly reduced (p less than 0.001) in the nerves of patients with severe diabetic neuropathy when compared to control subjects. Endothelial cell profile number and luminal perimeter were significantly increased in asymptomatic (p less than 0.01), (p less than 0.05) and severely neuropathic (p less than 0.001), (p less than 0.05) diabetic patients respectively. However, endothelial cell outer perimeter, a measure of capillary size, showed no significant increase in diabetic patients when compared with control subjects. An association was observed between neurophysiological and neuropathological measures of neuropathic severity. There was no significant correlation between the duration of diabetes and HbA1 levels with capillary pathology or with neuropathic severity. Very few abnormalities of muscle and skin correlated with neuropathic severity. However, all measures of nerve capillary pathology correlated significantly with neurophysiological and neuropathological measures of neuropathic severity.

Reactivation of creatine kinase activity by preincubation with buffered NAC diluent

We have shown that several commercial control sera containing reversibly inactivated creatine kinase are reactivated by pre-incubation in N-acetyl cysteine assay diluent. The increase in activity can proceed for up to 4 h. This reactivation is not seen in patients' sera even after storage for 14 days at -20 degrees C, 7 days at 4 degrees C, or 2 days at 20 degrees C, during which time no loss of activity was evident. This study brings into question the validity of using consensus values to standardise enzyme assays.

Seroepidemiological studies of HTLV-III antibody prevalence among selected groups of heterosexual Africans

T-lymphocyte subsets and human T-cell lymphotropic virus type III antibody prevalence were studied in African patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC), and in female prostitutes. African blood donors and healthy Zairian and Rwandese persons matched for age, sex, and annual income served as controls. Seropositivity was noted in 46 (87%) of 53 patients with AIDS, 29 (88%) of 33 patients with ARC, 67 (80%) of 84 prostitutes, and five (12.5%) of 40 and eight (15.5%) of 51 healthy controls and blood donors, respectively. Patients with AIDS and ARC had a significantly lower OKT4/OKT8 ratio than healthy African controls. These studies suggest that human T-cell lymphotropic virus type III infection has already spread extensively into the general African population and that female prostitutes could be an important human reservoir of AIDS virus in the heterosexual population.

Type-I and type-III HTLV antibodies in hospitalized and out-patient Zairians

Sera from 182 Zairians (99 females and 83 males), aged 5 to 71 years, including maternity and child care consultants, out-patients suffering from minor injuries and patients hospitalized for tuberculosis, malaria or trauma, were analyzed for specific antibodies to HTLV-I and HTLV-III. Following pre-screening by the ELISA technique, reactive sera were further analyzed for specificity to HTLV-I or HTLV-III antigens by competition and/or Western blotting experiments. African sera, possibly because they have higher immunoglobulin levels than US and European sera, are highly reactive in ELISA systems and confirmatory assays are essential to rule out false-positive results. Confirmed antibody prevalence for HTLV-I was 13.2% (II females and 13 males) and increased with age, suggesting continuous exposure to the virus throughout life. Confirmed antibody prevalence for HTLV-III was 6.0% (8 females and 3 males) and showed a peak age range between 21 and 40 years, suggesting heterosexual transmission. Individuals positive for HTLV-I antibodies were not the same as individuals positive for HTLV-III antibodies, suggesting that infection with one virus did not increase susceptibility to infection by the other virus. Further investigations of the epidemiology and of the immunovirology of HTLV-III in Zaire, in relation to acquired immuno-deficiency syndrome (AIDS)-associated pathologies, should enlighten the question of the significant percentage of HTLV-III-infected individuals who do not manifest symptoms of AIDS.

Experimental demyelinating optic neuropathy: a model for combined morphological and electrophysiological studies

A model is described for the morphological and electrophysiological study of demyelinative optic neuropathy in the rat. Cortical visual evoked potentials (VEPs) to flash stimuli were recorded before and after the intraneural microinjection of lysophosphatidyl choline (LPC) and galacto-cerebroside (Gal-C) antiserum. Progress was monitored by calculating the interocular latency differences (ILD) for the N40 and P60 components of the rat VEP, thus allowing a longitudinal evaluation of optic nerve function. Histological examination of the visual pathway using light and electron microscopy was performed at intervals through the course of the study. LPC produced a less selective lesion than did Gal-C antiserum. In lesions induced by the latter there was relatively little accompanying anoxal degeneration and subsequent remyelination was prominent. Control serum did not result in demyelination. This model should permit accurate electrophysiological and morphological correlations to be made during the developing and the reparative phases of demyelinative optic neuropathy and the assessment of potential therapeutic manoeuvres.

Cholinergic modification of glucose-induced biphasic insulin release in vitro

An in vitro system for perifusion of rat pancreatic islets has been utilized to define the effects of cholinergic agents on the dynamics of insulin release. In the absence of glucose the effects of either acetylcholine or acetyl-beta-methylcholine were minimal at concentrations up to 10(-5) mM. In the presence of low glucose concentration (2.4 mM), both of the muscarinic agents produced dose-dependent biphasic insulin release. Under these conditions significant insulin release was observed over both phases at concentrations of the muscarinic agents as low as 10(-8) mM. Further, the dose response curves relating muscarinic concentration to the total amount of insulin released in each of the two phases showed lack of parallelism between the curves. Nicotinic acid in concentrations up to 10(-5) mM had no effect on insulin release in the presence of 2.4 mM glucose. When the glucose concentration was increased to 16.4 mM, the effects of the muscarinic agents were significantly less than those observed in the presence of 2.4 mM glucose. This held true whether the effect was defined as absolute increment due to the muscarinic agent or as percentage of enhancement. Atropine inhibited insulin release induced by both acetylcholine and by 16.4 mM glucose. These data indicate that cholinergic stimulation can play a significant role in modifying insulin release patterns.