Plant regeneration through somatic embryogenesis from mature seed and young inflorescence of wild rice (Oryza perennis Moench)

Somatic embryogenesis in the wild rice species (Oryza perennis) was induced from cultured mature seeds and young inflorescences. Murashige and Skoog's (MS) medium supplemented with 2 mg/l 2,4-D and 0.2 mg/l BAP was used for induction of a compact, white nodular callus and somatic embryos. Plant regeneration occurred with the tranfer of the nodular callus to MS basal medium containing 0.5 mg/l IAA, 0.5 mg/l NAA, 4 mg/l BAP and 500 mg/l casein hydrolysate. The embryogenic nature of the callus from both explants was maintained over 10 subcultures for about 12 months. Plant regeneration with respect to the number of calli plated from the 6th to 10th passage varied from 80% to 60% for young inflorescence derived callus and from 75% to 69.8% for seed-derived callus.

Renal gluconeogenesis: axial and internephron heterogeneity and the effect of parathyroid hormone

To better understand the regulation of renal gluconeogenesis that occurs in the proximal nephron, glucose production rates from various substrates were determined in defined proximal tubule segments of the rat. Tubule segments tested were the S1 and S2 segments of superficial (SF) nephrons, the S1 segments of juxtamedullary (JM) nephrons, and the S3 segments. Glucose production (in decreasing order) was: from alpha-ketoglutarate, JM S1, SF S1, SF S2; from pyruvate, SF S2, JM S1, and SF S1; from glutamine, SF S1, JM S1; and from glutamate, SF S1 = JM S1. Little glucose was produced in the S3 segments. Glucose production from glutamate was lower than that from the other three substrates in JM S1, and glutamine was the best gluconeogenic substrate in SF S1. The effects of parathyroid hormone (PTH), a known stimulator of renal gluconeogenesis, and cAMP were examined using alpha-ketoglutarate as the substrate. Both stimulated glucose production in the S1 and S2 segments of the SF nephron. Although PTH stimulated adenylate cyclase in the S1 segments of the SF and JM nephrons, it had no effect on glucose production in the JM S1. Glucose production rose in the SF S1 and JM S1 in response to increasing concentrations of hydrogen or calcium ions, indicating that gluconeogenesis can be increased in these nephron segments. Differences may therefore be present in the cellular responses to PTH distal to cAMP formation in the nephron segments of the SF and JM nephrons. These findings show the presence of both axial and internephron heterogeneity of renal gluconeogenesis and suggest the difference in the effects of PTH on the function of SF and JM nephrons.

Effect of parathyroid hormone and calcium ions on substrate oxidation by isolated glomeruli of the rat

Effect of Ca2+ and parathyroid hormone (PTH) on 14 CO2 production from certain metabolic substrates by isolated glomeruli of rat kidney were examined. Increasing calcium concentration in the incubation medium inhibited 14CO2 production from 14C-labeled alpha-ketoglutarate and succinate, stimulated 14CO2 production from [1-14C]glucose and [1-14C]glutamate, but was without effect on that from [6-14C]glucose. PTH in the presence but not in the absence of Ca2+ inhibited 14CO2 production from labeled alpha-ketoglutarate and glutamate but not from labeled glucose. Additions of cyclic AMP as well as hormonal agents known to act directly on the glomureli, such as histamine, epinephrine, prostaglandin E2, vasopressin, angiotensin II and insulin, did not alter 14 CO2 production from labeled alpha-ketoglutarate. These data show the presence of calcium-dependent inhibitory actions on PTH on oxidation of alpha-ketoglutarate and glutamate which may be independent of cyclic AMP. These metabolic effects of PTH may underlie the alteration in the glomerular ultrafiltration coefficient and glomerular filtration induced by the hormone.

Adenylate cyclase and cell cyclic AMP of rat cortical thick ascending limb of Henle

Effects of parathyroid hormone (PTH), calcitonin (CT), vasopressin (VP), and glucagon (GL) on adenylate cyclase activity and cyclic AMP (cAMP) levels in isolated cortical thick ascending limbs of Henle's loop (CTAL) of the rat kidney were examined. PTH, CT, and VP each stimulated adenylate cyclase of this nephron segment in a dose-dependent manner. Stimulation of the enzyme activity was greatest with a maximal dose of PTH and least with VP. With maximal doses, the effects of PTH and CT were not additive; whether or not the effects of maximal doses of VP and PTH or CT were additive was not clear. All three hormones increase cAMP in intact CTAL ina dose-dependent manner. Maximal doses of PTH, CT, VP, and GL resulted in comparable rises in cell cAMP, and there was no additive effect. These data suggest that PTH and CT may stimulate the same adenylate cyclase moieties, whereas VP may stimulate distinct enzyme moieties, and that these three peptide hormones as well as GL definitely act on the same cell group in rat CTAL. Thus, it is possible that these hormones may induce qualitatively similar effects on CTAL functions if such effects are mediated by cAMP.

Substrate oxidation by isolated single nephron segments of the rat

Substrate oxidation was assessed by measuring 14CO2 production from 14C-labeled substrates in proximal convoluted tubules (PCT), medullary (MTAL), and cortical (CTAL) thick ascending limb of Henle, nephron segments rich in mitochondria and characterized by active solute transport. PCT, MTAL, and CTAL were dissected from the outer cortex, outer medulla, and the medullary rays of the cortex, respectively, of collagenase-treated rat kidney slices. Tubules were incubated at 37 degrees C in 150 microliters of Krebs-Ringer-bicarbonate buffer (pH, 7.4) with 14C-labeled substrate. 14CO2 production was linear up to 4 and 2 hours in PCT and MTAL, respectively. Freeze-thawing of the tubules markedly decreased 14CO2 production, and the addition of cyanide completely abolished it. The PCT demonstrated marked 14CO2 production from labeled succinate, 2-oxoglutarate, glutamate, glutamine, and malate (approximately 10 to 45 pmoles/mm/hr) and moderate 14CO/ production from citrate (approximately 3 pmoles/ml/hr). Little 14CO2 was released from labeled glucose and lactate in PCT. These results are consistent with the existence of gluconeogenesis in this nephron segment. By contrast, MTAL and CTAL oxidized glucose, 2-oxoglutarate, lactate, glutamate, and glutamine, but not malate, succinate, and citrate. The pentose shunt pathway accounted for approximately half of the 14CO2 produced from 1-14C glucose in MTAL and CTAL. Palmitate oxidation occurred in MTAL and CTAL but minimally in PCT. The results demonstrate a distinct pattern of substrate oxidation in PCT, MTAL, and CTAL where oxidative metabolism is critical to support active solute transport.

Nutritional status of the elderly: dietary and biochemical findings

The nutritional status of 100 elderly women and men was evaluated in terms of their dietary nutrient intakes and selected biochemical measurements. Calcium, vitamin A, and thiamin were the dietary nutrients most likely to be deficient, especially with women. Nutrient supplements, taken by 27 subjects, were generally inappropriate and frequently excessive. Forty-one percent of the group had low serum protein concentrations. Values for hematocrit, hemoglobin, serum iron and ascorbic acid, plasma vitamin A and carotene were in acceptable ranges for 90% of the subjects. Biochemical values were not significantly correlated with dietary nutrients except for hemoglobin with dietary iron and serum ascorbic acid with dietary ascorbic acid. In a subsample of 20 persons, both dietary and serum folate values were low. Twenty subjects who lived in a retirement community that provided one major meal daily consumed less food than those who were completely independent but had similar biochemical values.

Binding of 125I-insulin to the isolated glomeruli of rat kidney

To investigate a possible action of insulin on the glomerulus, the binding 125I-insulin to the isolated glomeruli prepared from rat kidney was examined. When incubated at 22 degrees C, 125I-insulin binding proceeded with time and reached a steady state at 45 min at which time nonspecific binding was less than 25% of total binding. A small fraction of 125I-insulin was degraded during incubation. This binding was specific to insulin in that it was inhibited by unlabeled porcine and beef insulins and to a lesser extent by porcine proinsulin and desalanine-desasparagine insulin, but not by glucagon, parathyroid hormone, vasopressin, calcitonin, and angiotensin II. Increasing concentrations of nonlabeled insulin displaced 125I-insulin binding in a dose-dependent fashion. Scatchard plot of the data was curvilinear consistent with either two classes of receptors with different affinities or a single class of receptors that demonstrate negative cooperativity. The addition of excess nonlabeled insulin to the glomeruli preincubated with 125I-insulin resulted in a rapid dissociation of approximately or equal to 70% of bound 125I-insulin. Insulin decreased the increments in glomerular cyclic AMP levels by epinephrine and by prostaglandin E2, but not those by histamine. These data showed the presence of specific insulin receptors in the glomeruli, and that insulin action may be, at least in part, through modulation of glomerular cyclic AMP concentrations. Such action of insulin may underlie the alteration in glomerular ultrafiltration and the glomerular ultrafiltration and the development of glomerular lesions in diabetes mellitus, a disease in which insulin deficiency or the tissue resistance to insulin exists.