The sympathetic nervous system in diabetic neuropathy. A clinical and pathological study

Tests of autonomic function were performed on 16 subjects with diabetic neuropathy. Abnormal sweating occurred in 10/10 (100 per cent), postural hypotension in 7/16 (44 per cent), an abnormal Valsalva ratio in 7/11 (64 per cent), and denervation hypersensitivity to phenylephrine in 2/8 (25 per cent) of patients tested. A quantitative assessment of baroreceptor function was made. In diabetics, there was a reduced resting heart period, heart period range and mean gain. Quantitative histological studies were performed on the greater splanchnic nerves removed at autopsy from 9 control subjects and from 8 subjects with diabetic neuropathy. The fibre density was significantly reduced in the greater splanchnic nerve of diabetics. The predominant pathology on teased fibre preparations was that of demyelination. Disordered blood pressure control in diabetes correlated with the pathological abnormalities in the sympathetic nervous system. Light and electronmicroscopic studies were performed on the sural nerves of 2 diabetic subjects with autonomic dysfunction. The predominant change was active axonal degeneration affecting mainly unmyelinated and small myelinated fibres.

Limitation of acetylene reduction (nitrogen fixation) by photosynthesis in soybean having low water potentials

The role of photosynthesis and transpiration in the desiccation-induced inhibition of acetylene reduction (nitrogen fixation) was investigated in soybean (Glycine max [L.] Merr. var. Beeson) using an apparatus that permitted simultaneous measurements of acetylene reduction, net photosynthesis, and transpiration. The inhibition of acetylene reduction caused by low water potentials and their aftereffects could be reproduced by depriving shoots of atmospheric CO(2) even though the soil remained at water potentials that should have favored rapid acetylene reduction. The inhibition of acetylene reduction at low water potentials could be partially reversed by exposing the shoots to high CO(2) concentrations. When transpiration was varied independently of photosynthesis and dark respiration in plants having high water potentials, no effects on acetylene reduction could be observed. There was no correlation between transpiration and acetylene reduction in the CO(2) experiments. Therefore, the correlation that was observed between transpiration and acetylene reduction during desiccation was fortuitous. We conclude that the inhibition of shoot photosynthesis accounted for the inhibition of nodule acetylene reduction at low water potentials.

Acetylene reduction (nitrogen fixation) and metabolic activities of soybean having various leaf and nodule water potentials

An apparatus was designed that permitted acetylene reduction (N(2) fixation) by root nodules to be measured in situ simultaneously with net photosynthesis, dark respiration, and transpiration of the shoot in soybean plants (Glycine max [L.] Merr. var. Beeson). Tests showed that acetylene reduction was linear with time for at least 5 hours, except for the first 30 to 60 minutes. Endogenous ethylene production did not affect the measurements. Successive determinations of acetylene reduction could be made without apparent aftereffects on the plant.This apparatus was used to investigate the effects of soil flooding and desiccation on acetylene reduction under conditions where soil, nodule, and leaf water potentials could be measured. No acetylene reduction was detectable in flooded soil or in soil desiccated to a water potential of -19.5 bars. Between these extremes, acetylene reduction displayed a sharp optimum. Removing the soil eliminated the inhibitory effects of flooding, suggesting that rates of gas exchange were restricted between the nodules and the atnosphere at soil water potentials above -2 bars.As the soil desiccated further, acetylene reduction decreased, and the decrease was correlated with decreases in photosynthesis and transpiration. Although dark respiration was inhibited, it was not affected to the extent that acetylene reduction, photosynthesis, or transpiration were. Consequently, it was concluded that photosynthesis, transpiration, or some direct effect on the nodules other than that caused by respiration were most likely to account for the inhibition of acetylene reduction at soil water potentials below -2 bars.

Diurnal variation in algal acetylene reduction (nitrogen fixation) in situ

Diurnal variation in algal nitrogen fixation was studied in Lake Mendota, Wisconsin, during the summers of 1971 to 1973. Approximately two-thirds of the daily acetylene reduction in the surface decimeter occurred before noon. The decline in acetylene reduction (nmoles/liter.hr) near midday was partially because the algae relocated themselves at greater depths. However, acetylene reducing activity (nmoles per A(663) unit chlorophyll a per hour) also decreased as midday approached. Occasionally algae would resurface near the end of the day. On average, acetylene reduction (nmoles per liter per hour) was maximum at about 0900 Central standard time in the top decimeter, and acetylene reduction between 0830 and 0930 Central standard time represented 13% of the total daily acetylene reduction. Furthermore, acetylene reduction in the top decimeter, on average, represented 3.6% of the total acetylene reduction in the column. Calculation of the contribution by nitrogen fixation to a lake's fixed nitrogen budget is discussed.

The inhibition of soybean metabolism by cadmium and lead

Lead (300 mum) and cadmium (18 mum) inhibit pod fresh weight in soybeans (Glycine max L.) by 35%. Eighteen micromolar cadmium caused a 30% decline in nitrogenase activity by day 52 (the day on which maximum activity was measured) and a 71% inhibition by day 59. The heavy metals depressed photosynthetic rates; when photosynthesis was depressed by 60%, as measured on the day of peak photosynthesis activity, carbohydrate did not accumulate in the nodules. The reduction of pod fresh weight correlated with the effect of lead and cadmium on several other aspects of plant metabolism (shoot, root, leaf, and nodule dry weight; nodule ammonia, protein and carbohydrate content).

Epsilon-adenylylated glutamine synthetase: an internal fluorescence probe for enzyme conformation

A fluorescent derivative of ATP, epsilon-ATP, was used to adenylylate glutamine synthetase (EC 6.3.1.2) from Escherichia coli enzymatically. The epsilon-adenylylated enzyme exhibits similar catalytic properties and inhibitor susceptibility to those of the naturally adenylylated enzyme. The fluorescence properties of the epsilon-adenosine and of tryptophan residues of the enzyme were used to study ligand-induced conformational changes involving alterations of the tryptophan regions and the adenylylation site of the protein. Binding of Mn(2+) to the epsilon-adenylylated enzyme is accompanied by a decrease of epsilon-adenosine fluorescence as compared to the effect observed for the Mg(2+) binding. An ADP binding study shows that at low ADP concentration, ADP causes enhancement of the tryptophan fluorescence only, reflecting the binding to unadenylylated subunits; and at high ADP concentration, ADP causes not only enhancement of the fluorescence, but also a quenching of the fluorescence of enzyme-bound epsilon-AMP, reflecting binding to the adenylylated subunits. Dissociation constants calculated from these fluorescence changes agree well with those determined from binding studies of ADP to adenylylated and unadenylylated enzymes. Binding of the feedback inhibitor, alanine, to Mn(2+)-dependent glutamine synthetase causes enhancement of the epsilon-AMP fluorescence, from which a dissociation constant of 1.5 mM was calculated for the inhibitor. The fluorescence changes observed due to ligands binding suggest that Mg(2+) and Mn(2+) stabilize different conformational states of the enzyme.

Rates of GDP-induced and GTP-induced depolymerization of glutamate dehydrogenase: a possible factor in metabolic regulation

The rate of the depolymerization of beef liver glutamate dehydrogenase induced by coenzyme and the purine nucleotides guanosine 5'-diphosphate and guanosine 5'-triphosphate, which are potent inhibitors of enzymatic activity, has been measured by rapid light scattering techniques and by absorbancy changes with stop flow. It is shown that the rate constant for this process may vary from several milliseconds to several seconds depending upon the nucleotides used. The widely varying rate constants for the nucleotide-induced depolymerization may serve a role in determining the nature of the regulation of enzyme activity by nucleotides. Depolymerization induced by guanosine 5'-diphosphate in the presence of diphosphopyridine nucleotide is slower than in the presence of triphosphopyridine nucleotide as coenzyme, and this difference is apparently due to the isomerization of the enzyme as a result of diphosphopyridine nucleotide binding to a second, nonactive site. This binding, as well as binding of the coenzyme to the active site, may be conveniently measured by a purine nucleotide-induced spectral shift in the coenzyme absorption spectrum. It is also shown that complete depolymerization of the enzyme in the presence of guanosine 5'-triphosphate is accomplished by about half saturation of the coenzyme active sites (6-8 active "monomer").

Immunopathology of NZB/BL mice. VI. Virus separable from spleen and pathogenic for Swiss mice

Hemolytic disease characterized by slight anemia, reticulocytosis, hemosiderosis, extramedullary hematopoiesis, and positive indirect antiglobulin (Coombs') tests and renal disease with proteinuria, hypoalbuminemia, and glomerular lesions were produced in Swiss mice by neonatal intraperitoneal inoculation of cell-free filtrates prepared from the spleens of old NZB/Bl mice. Lymphoid cell and plasma cell hyperplasia as well as hypergammaglobulinemia occurred in some of these inoculated mice. Type "C" murine oncogenic virus-like particles, indistinguishable from those previously described (1), were shown by electron microscopic study to be present in distinctive locations, notably in the basal foldings of convoluted tubules in the kidneys of a newborn NZB/Bl mouse, old NZB/Bl mice, a CBA x NZB F(1) hybrid mouse, and a Swiss mouse inoculated with NZB/Bl spleen cell-free filtrate. These observations point to two (perhaps related) circumstances which may be requisites for the pathogenic action of this newly discovered virus within and outside the strain NZB: infection of newborn, or infant, mice; persistent, possibly tolerant, infection of adult mice.

Immunopathology of NZB/BL mice. V. Viruslike (filtrable) agent separable from lymphoma cells and identifiable by electron microscopy

A filtrable agent separable from transplantable malignant lymphomas of NZB/Bl mice was capable, upon inoculation into preweanling NZB/Bl mice, of inducing lymphoid cell hyperplasia, hypergammaglobulinemia, proteinuria, hypoalbuminemia, and pathological changes (focal membranous glomerulonephritis) of kidneys-renal functional and structural changes qualitatively similar to those of spontaneous occurrence in older NZB/Bl mice. Viruslike particles with close resemblance to the typical "C" type murine oncogenic virus particles were identified by means of electron microscopy in NZB/Bl mouse tissues and cells, including malignant lymphoma cells, benign lymphoid cells of thymus and spleen, epithelial cells of renal tubules, and extracellular sites. The relevance of these observations, the first of their kind dealing with NZB/Bl mice, is discussed in relation to the several immunopathological disorders which characterize this strain of mice.