Water deficits and hydraulic limits to leaf water supply.

Many aspects of plant water use -- particularly in response to soil drought -- may have as their basis the alteration of hydraulic conductance from soil to canopy. The regulation of plant water potential (Psi) by stomatal control and leaf area adjustment may be necessary to maximize water uptake on the one hand, while avoiding loss of hydraulic contact with the soil water on the other. Modelling the changes in hydraulic conductance with pressure gradients in the continuum allows the prediction of water use as a function of soil environment and plant architectural and xylem traits. Large differences in water use between species can be attributed in part to differences in their 'hydraulic equipment' that is presumably optimized for drawing water from a particular temporal and spatial niche in the soil environment. A number of studies have identified hydraulic limits as the cause of partial or complete foliar dieback in response to drought. The interactions between root:shoot ratio, rooting depth, xylem properties, and soil properties in influencing the limits to canopy water supply can be used to predict which combinations should optimize water use in a given circumstance. The hydraulic approach can improve our understanding of the coupling of canopy processes to soil environment, and the adaptive significance of stomatal behaviour.

Steady-state isotopic fractionation in branched pathways using plant uptake of NO3- as an example.

A steady-state isotopic discrimination model is developed for material transfer between a single source and two distinct sinks arising from an internal branching of the uptake pathway. Previous analyses of isotopic discrimination in multistep processes are extended to include the effects of the interacting sinks. The theory is first developed as a set of generic expressions allowing for flexibility in the definition of intermediate pools in all parts of the branched transport pathways, and then applied to a case study of nitrate uptake by plants. The isotopic composition of assimilated nitrate may be evaluated with the model for either contrasting root versus shoot assimilate pools, each with a unique isotopic signature, or as a single mean value for whole-plant nitrate reduction. The theory is further developed to indicate how isotopic measurements may be used to infer (i) efflux:influx ratios at the root plasma membrane, (ii) partitioning of assimilate capture between root and shoot reduction sites, and (iii) mixing of root and shoot assimilate pools in sink tissues due to whole-plant circulation of organic nitrogen in both xylem and phloem.

Effect of intensive glycemic control on microalbuminuria in type 2 diabetes. Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type 2 Diabetes Feasibility Trial Investigators.

OBJECTIVE: Microalbuminuria can reflect the progress of microvascular complications and may be predictive of macrovascular disease in type 2 diabetes. The effect of intensive glycemic control on microalbuminuria in patients in the U.S. who have had type 2 diabetes for several years has not previously been evaluated. RESEARCH DESIGN AND METHODS: We randomly assigned 153 male patients to either intensive treatment (INT) (goal HbA(1c) 7.1%) or to standard treatment (ST) (goal HbA(1c) 9.1%; P = 0.001), and data were obtained during a 2-year period. Mean duration of known diabetes was 8 years, mean age of the patients was 60 years, and patients were well matched at baseline. We obtained 3-h urine samples for each patient at baseline and annually and defined microalbuminuria as an albumin:creatinine ratio of 0.03-0.30. All patients were treated with insulin and received instructions regarding diet and exercise. Hypertension and dyslipidemia were treated with similar goals in each group. RESULTS: A total of 38% of patients had microalbuminuria at entry and were evenly assigned to both treatment groups. INT retarded the progression of microalbuminuria during the 2-year period: the changes in albumin:creatinine ratio from baseline to 2 years of INT versus ST were 0.045 vs. 0.141, respectively (P = 0.046). Retardation of progressive urinary albumin excretion was most pronounced in those patients who entered the study with microalbuminuria and were randomized to INT. Patients entering with microalbuminuria had a deterioration in creatinine clearance at 2 years regardless of the intensity of glycemic control. In the group entering without microalbuminuria, the subgroup receiving ST had a lower percentage of patients with a macrovascular event (17%) than the subgroup receiving INT (36%) (P = 0.03). Use of ACE inhibitors or calcium-channel blockers was similarly distributed among the groups. CONCLUSIONS: Intensive glycemic control retards microalbuminuria in patients who have had type 2 diabetes for several years but may not lessen the progressive deterioration of glomerular function. Increases in macrovascular event rates in the subgroup entering without albuminuria who received INT remain unexplained but could reflect early worsening, as observed with microvascular disease in the Diabetes Control and Complications Trial.

Two years of intensive glycemic control and left ventricular function in the Veterans Affairs Cooperative Study in Type 2 Diabetes Mellitus (VA CSDM).

OBJECTIVE: The Veterans Affairs Cooperative Study in Type 2 Diabetes Mellitus (VA CSDM) was a multicenter randomized prospective study of 153 male type 2 diabetic patients to assess the ability to sustain clinically significant glycemic separation between intensive and standard treatment arms. A trend toward an excess of combined cardiovascular events in the intensive treatment arm of this trial was reported earlier. The present analysis was done to evaluate the effect of 2 years of intensive glycemic control on the left ventricular (LV) function. RESEARCH DESIGN AND METHODS: The patients were randomized to intensive step treatment with insulin alone or with sulfonylurea (intensive treatment arm [INT], n = 75) or to standard once-daily insulin injection (standard treatment arm [STD], n = 78) treatment. A total of 136 patients (standard treatment arm [STD], n = 70; INT, n = 66) had radionuclide ventriculography at entry and at 24 months for the assessment of LV function. RESULTS: There was no difference in the mean LV ejection fraction (at entry: STD 57.1+/-9.51%; INT 58.1+/-8.7%; at 24 months: STD 57.3+/-10.8%, INT 59.5+/-10.7%), peak filling rate (at entry: STD 2.6+/-0.7 end diastolic volume per second, INT 2.4+/-0.8 end diastolic volume per second; at 24 months: STD 2.7+/-1.0 end diastolic volume per second, INT 2.5+/-0.7 end diastolic volume per second), or time to peak filling rate (at entry: STD 195.3+/-69.5 ms, INT 185.6 +/-62.4 ms; at 24 months: STD 182.6+/-64.8 ms, INT 179.2+/-61.2 ms) between the 2 treatment arms. A subgroup analysis of 104 patients (STD, n = 53; INT, n = 51) that omitted individuals with intervening cardiac events/revascularization or a change in cardioactive medications also showed no difference in the LV function at entry and at 24 months between the 2 groups. Abnormal LV ejection fraction at baseline predicted cardiac events (interval between cardiac beats [RR] = 2.5). CONCLUSIONS: Two years of intensive glycemic control does not affect the LV systolic or diastolic function in patients with type 2 diabetes.

Variation in hydraulic architecture and gas-exchange in two desert sub-shrubs, Hymenoclea salsola (T. & G.) and Ambrosia dumosa (Payne).

Adjustment of hydraulic architecture in response to environmental conditions was studied in two warm-desert sub-shrubs, Hymenoclea salsola and Ambrosia dumosa, both at the level of genetic adaptation along a climatic gradient and plastic response to immediate growth conditions. Individuals of both species originating from southern populations developed higher leaf-specific hydraulic conductance in the common greenhouse than individuals from northern populations. Hydraulic conductance was higher in plants grown at high temperature, but did not vary as a function of growth relative humidity. Hydraulic conductance was not correlated within species with individual variation in vessel diameter, cavitation vulnerability, or root:shoot ratio, but was strongly, negatively correlated with the fraction of total plant biomass allocated to leaves. For both species, stomatal conductance (g s) at high leaf-to-air vapor pressure difference (ν) was tightly correlated with variability in hydraulic conductance, as was the sensitivity of stomatal closure to increasing ν. Experimentally increasing shoot water potential by soil pressurization, under conditions where high ν had already caused stomatal closure, led to substantial stomatal reopening in both species, but recovery was significantly higher in H. salsola. Hydraulic conductance was higher in H. salsola than A. dumosa. H.salsola also differed from A. dumosa by being a representative of a highly specialised group of desert shrubs which use the twigs as a major photosynthetic organ. The southern population of H. salsola produced far fewer leaves and relied much more heavily on twig photosynthesis than the northern population. At the whole-plant level, increased reliance on twig photosynthesis was associated with higher leaf-specific hydraulic conductance, but equivalent whole-plant photosynthesis on either a dry weight (µmol CO2 g-1) or nitrogen basis (µmol CO2 g-1)). This suggests that twig photosynthesis might be one way of increasing hydraulic conductance per unit photosynthetic canopy by increasing allocation to an organ which simultaneously performs photosynthetic, support, and transport functions.

Why Canny's theory doesn't hold water.

A critique of Martin Canny's theory of water transport supported by tissue pressure is given with reference to basic principles of cellular water relations and biomechanics. It is shown that the application of tissue pressure in Canny's theory is neither internally consistent nor compatible with basic biophysics. Canny's translation of tissue pressure into an altered steady-state pressure in the xylem conduits has no defensible mechanism, relying instead on untenable action-at-a-distance and poor definitions. Tissue pressure itself, as defined by Canny and illustrated by the example of a turgid leaf, may well exist. However, it cannot function in whole-plant processes as envisioned by Canny, nor can it exist in the magnitude his theory would require. Rigid outer tissue layers containing internal pressures of the magnitude postulated by Canny would require a tensile strength quite incompatible with the observed biological materials. A simple application of La Place's Law illustrates that this is an issue of scale and that the turgor generated by osmotic potentials must be balanced primarily at the cellular level, and not the tissue level.

The effects of intensive glycemic control on neuropathy in the VA cooperative study on type II diabetes mellitus (VA CSDM).

To determine whether a difference in HbA(1c) could be safely sustained between a standard therapy (STD) arm and an intensive therapy (INT) arm, while maintaining HbA(1c) levels in both arms within a range acceptable in community practice. The effects of intensive treatment on various parameters were studied in this feasibility trial. We report here the results of 24 months of INT on peripheral and autonomic neuropathy.A prospective trial was conducted in five medical centers in 153 men of 60 +/- 6 years of age who had a known diagnosis of diabetes for 7.8 +/- 4 years. They were randomly assigned to a standard insulin treatment group (one morning injection per day) or to an intensive therapy group designed to attain near-normal glycemia and a clinically significant separation of glycohemoglobin from the standard arm. A four-step plan was used in the intensive therapy group along with daily self-monitoring of glucose: (1) an evening insulin injection, (2) the same injection adding daytime glipizide, (3) two injections of insulin alone, and (4) multiple daily injections. Peripheral neuropathy was diagnosed clinically by a history and physical examination, and by abnormal autonomic neuropathy Valsalva ratio (VR < 1.2) and RR variation (RRV < 10). An average HbA(1c) separation of 2.07% was achieved with INT, having HbA(1c) at or below 7.3% (p = 0. 001 versus STD). Baseline prevalence of peripheral neuropathy was 53% in STD, and 48% in INT. By 24 months, the prevalence increased to 69% in STD (p = 0.005 versus baseline), and to 64% in INT (p = 0. 008 versus baseline, but no different than STD). Though INT did not reverse all elements of peripheral neuropathy, there was a decreased prevalence of cranial neuropathy (p = 0.053 versus STD) and more frequent preservation of touch sensation in the upper extremities (p = 0.03 versus STD) in INT. At baseline, an abnormal Valsalva ratio and/or RR variation was seen in 38% of STD and 31% of INT. By 24 months in STD, the prevalence rose to 55% (p = 0.0067 versus baseline), and in INT, to 48% (p = 0.012 versus baseline and no different from STD). The prevalence of erectile dysfunction increased from 53% at baseline to 73% at 2 years, p = 0.002 in STD, and from 51% to 73% at 2 years (p = 0.003 versus baseline) and no different from STD. There was no change in the frequency of abnormal gastrointestinal or sweating symptoms. Our conclusion was that 2 years of meticulous glycemic control did not decrease overall prevalence of peripheral or autonomic neuropathy. In fact, the prevalence rose equivalently and significantly in both treatment arms. There was some benefit, however, in decreased frequency of cranial neuropathy and better preservation of touch sensation in INT.

Ethnic differences in the glycemic response to exogenous insulin treatment in the Veterans Affairs Cooperative Study in Type 2 Diabetes Mellitus (VA CSDM).

OBJECTIVE: The Veterans Affairs Cooperative Study in Type 2 Diabetes Mellitus was conducted in NIDDM patients to determine if a significant difference in HbA1c could be achieved between groups receiving standard and intensive treatment. We observed differences in the response to exogenous insulin between African-Americans and other intensively treated patients. Therefore, we assessed the variations of response and correlated factors that might explain such differences. RESEARCH DESIGN AND METHODS: One hundred fifty-three men aged 40-69 years with NIDDM for < or = 15 years were randomized to either the standard therapy (n = 78) or the intensive therapy (n = 75) arm. Of the 75 patients in the intensive therapy group, 57 completed the study on insulin therapy alone. Of these, 18 were African-Americans and 39 were non-African-Americans. We conducted an analysis of the data collected to determine differences in baseline characteristics, glycemic response, insulin requirement, body weight, exercise, and basal C-peptide level, factors that may explain a difference in response to insulin therapy. RESULTS: Glycemic control improved in all patients with intensive insulin therapy. African-Americans achieved a greater improvement in HbA1c compared with non-African-Americans with a similar increment in insulin. This difference could not be explained by differences in body weight, activity, concomitant use of other medicines, or insulin-secretory capacity of the pancreas. CONCLUSIONS: We conclude that ethnic differences may exist in the response to insulin therapy. A knowledge of such differences may aid in achieving good glycemic control, especially since minorities have a greater prevalence of and burden from the microvascular complications of diabetes.

Response to intensive therapy steps and to glipizide dose in combination with insulin in type 2 diabetes. VA feasibility study on glycemic control and complications (VA CSDM).

OBJECTIVE: The feasibility study for the VA Cooperative Study on Glycemic Control and Complications in Type 2 Diabetes (VA CSDM) prospectively studied 153 insulin-requiring type 2 diabetes patients, randomized between an intensively treated arm and a standard treatment arm during a mean follow-up of 27 months. The glycemic response to each of the progressive, sequential phases of insulin treatment was assessed, along with the incidence of hypoglycemic reactions and the relative efficacy of different doses of glipizide in combination with fixed doses of insulin. RESEARCH DESIGN AND METHODS: Five medical centers participated; half of the patients were assigned to the intensive treatment arm aiming for normal HbA1c levels. Age of patients was 60 +/- 6 years, duration of diabetes 8 +/- 3 years, and BMI 30.7 +/- 4 kg/m2. A four-step management technique was used, with patients moving to the next step if the operational goals were not met: Phase I, evening intermediate or long-acting insulin; phase II, added day-time glipizide; phase III, two injections of insulin alone; and phase IV, multiple daily insulin injections. Home glucose monitoring measurements were done twice daily and at 3:00 A.M. once a week. Hypoglycemic reactions and home glucose monitoring results were recorded and counted in each of the treatment phases. RESULTS: Baseline HbA1c was 9.3 +/- 1.8%, and fasting plus serum glucose was 11.4 +/- 3.3 mmol/1. Fasting serum glucose fell to near normal in phase I, and remained so in the other treatment phases. An HbA1c separation of 2.1% between the arms was maintained during the course of the study, while the intensive arm kept HbA1c levels below 7.3% (P = 0.001). Most of the decrease in HbA1c occurred with one injection of insulin alone (phase I, -1.4%) or adding day-time glipizide (phase II, -1.9% compared with baseline). HbA1c did not decrease further after substituting two injections of insulin alone, with twice the insulin dose. Multiple daily injections resulted in an additional HbA1c fall (-2.4% compared with baseline). However, two-thirds of the patients were still on one or two injections a day at the end of the study. Changes in home glucose monitoring levels paralleled those of the HbA1c, as did the increments in number of reported hypoglycemic reactions, virtually all either "mild" or "moderate" in character. For the combination of glipizide and insulin (phase II), the only significant effect was obtained with daily doses up to 10 mg a day; there were no significant additional benefits with up to fourfold higher daily doses, and HbA1c levels had an upward trend with doses > 20 mg/day. CONCLUSIONS: A simple regime of a single injection of insulin, alone or with glipizide, seemed sufficient to obtain clinically acceptable levels of HbA1c for most obese, insulin-requiring type 2 diabetes patients. Further decrease of HbA1c demanded multiple daily injections at the expense of doubling the insulin dose and the rate of hypoglycemic events. In combination therapy, doses of glipizide > 20 mg/day offered no additional benefit.

Effect of decreased plasma low-density lipoprotein levels on adrenal and testicular function in man.

OBJECTIVE: The study assessed whether serum LDL cholesterol levels affect adrenal and Leydig cell function in man. DESIGN AND METHODS: A 24-h continuous ACTH infusion was performed in 15 consecutive chronically ill patients. Serum cortisol and DHEA-s were measured at baseline and at 3, 6, 12, 20, and 24 h during the infusion. Fasting serum lipoprotein levels including LDL cholesterol, HDL cholesterol as well as FSH, LH, total and free testosterone concentrations were also measured on the baseline morning samples prior to the infusion. RESULTS: The initial 3 and 6 h percent rise in cortisol values during 24 h ACTH infusion were significantly diminished in patients with LDL-C values < 1.55 mmol/L as compared with patients with higher LDL-C levels (127 +/- 17% (SE) vs. 199 +/- 31% (SE); p < 0.02 and 115 +/- 17% vs. 213 +/- 32%; p < 0.02. However, the 24-h areas of cortisol under the curve were comparable in the 2 groups. Basal and ACTH stimulated DHEA-s levels and percent increases tended to be lower in the low LDL-C group but the differences were not statistically significant. The mean total testosterone was lower in the low LDL-C group (5.30 +/- 1.78 vs. 15.60 +/- 1.95 nmol/L; p < 0.0005). Free testosterone levels were also lower in the low LDL-C group (0.03 +/- 0.009 nmol/L vs. 0.08 +/- 0.01 nmol/L; p < 0.001). Five of six patients with low LDL-cholesterol had low testosterone values, but variable LH levels. CONCLUSIONS: Our results suggest that severe acquired LDL cholesterol insufficiency impairs slightly the initial glucocorticoid response to ACTH stimulation but not the overall cortisol production during sustained ACTH stimulation. It also may contribute to the reduction in testosterone seen in chronically ill patients.

Cardiovascular events and correlates in the Veterans Affairs Diabetes Feasibility Trial. Veterans Affairs Cooperative Study on Glycemic Control and Complications in Type II Diabetes.

BACKGROUND: The risks and benefits of intensive therapy in non-insulin-dependent diabetes mellitus (NIDDM) need to be defined. In preparation for a long-term trial, a feasibility study of 153 men in 5 medical centers compared standard vs intensive insulin therapy. OBJECTIVE: To assess the rate of development of new cardiovascular events and their correlates. METHODS: Patients with a mean +/- SD age of 60 +/- 6 years and diagnosis of NIDDM for 7.8 +/- 4.0 years were randomly assigned to a standard (1 insulin injection every morning) or to an intensive treatment arm (stepped plan from 1 evening injection of insulin, alone or with glipizide, to multiple daily injections) designed to attain near-normal glycemia levels. A 2.07% separation of glycosylated hemoglobin (HbA1c) was sustained for a mean follow-up of 27 months (P < .001). Predefined cardiovascular events were assessed by a committee unaware of treatment assignment. RESULTS: Mild and moderate hypoglycemic events were more frequent in the intensive than in the standard treatment arm (16.5 vs 1.5 per patient per year, respectively). Mean insulin dose was 23% lower in the standard treatment arm (P < .001). There were 61 new cardiovascular events in 24 patients (32%) in the intensive treatment arm and in 16 patients (20%) in the standard treatment arm (P = .10). There was no difference in total and cardiovascular mortality (n = 5 and n = 3 in the intensive and standard treatment arms, respectively) or in new events in patients with cardiovascular history (n = 10 in each arm). In Cox regression analysis, the only significant correlate for new cardiovascular events was previous cardiovascular disease (P = .04). Entering in the analysis any baseline cardiovascular abnormality, the regression model indicated a lower HbA1c level prior to the event as the only correlate for new cardiovascular events (P = .05). CONCLUSION: A long-term prospective trial is needed to assess the risk-benefit ratio of intensive insulin therapy for NIDDM in patients who require it.

Glyburide increases the secretion, tissue uptake, and action of insulin in conscious normal dogs.

The action of glyburide on glucose homeostasis involves pancreatic and extrapancreatic mechanisms. The relative importance of each of these processes in the hypoglycemic response to sustained administration of glyburide is unknown. In addition, the effect of this drug on the hepatic extraction of insulin is controversial. This investigation uses direct techniques in conscious normal dogs to examine the impact of glyburide therapy (2.5 mg twice daily for 4 weeks) on glucose homeostasis. Preparatory surgery included placement of Doppler flow probes on hepatic vessels and insertion of catheters in carotid artery, portal vein, hepatic vein, and renal vein. After recovery from surgery, animals underwent an intravenous glucose tolerance test ([IGTT] 0.3 g - kg (-1) intravenous glucose bolus) and an insulin infusion clamp test ([IICT] 2 mU - kg (-1) - min (-1) intravenous insulin during 150 minutes) followed by glyburide therapy. After 4 weeks, the IGTT and IICT were repeated. Glyburide increased the insulin secretory response during the late phase of the IGTT and augmented glucose clearance during the IICT. Hepatic extraction of insulin was also stimulated by glyburide. We conclude that the hypoglycemic action of long-term glyburide administration involves stimulation of both insulin secretion by the pancreas and glucose disposal by peripheral tissues. In addition, glyburide augments the extraction of insulin by the liver, and such an effect might prevent the development of sustained high levels of insulin in blood perusing peripheral tissues.

Veterans Affairs Cooperative Study on glycemic control and complications in type II diabetes (VA CSDM). Results of the feasibility trial. Veterans Affairs Cooperative Study in Type II Diabetes.

OBJECTIVE: It is not clear whether intensive pharmacological therapy can be effectively sustained in non-insulin-dependent diabetes mellitus (NIDDM). The relative risks and benefits of intensive insulin therapy in NIDDM are not well defined. Accordingly, we designed a feasibility study that compared standard therapy and intensive therapy in a group of NIDDM men who required insulin due to sustained hyperglycemia. RESEARCH DESIGN AND METHODS: A prospective trial was conducted in five medical centers in 153 men of 60 +/- 6 years of age who had a known diagnosis of diabetes for 7.8 +/- 4 years. They were randomly assigned to a standard insulin treatment group (one morning injection per day) or to an intensive therapy group designed to attain near-normal glycemia and a clinically significant separation of glycohemoglobin from the standard arm. A four-step plan was used in the intensive therapy group along with daily self-monitoring of glucose: 1) an evening insulin injection, 2) the same injection adding daytime glipizide, 3) two injections of insulin alone, and 4) multiple daily injections. Patient accrual and adherence, glycohemoglobin (HbA1c), side effects, and measurements of endpoints for a prospective long-term trial were assessed. RESULTS: Accrual goals were met, mean follow-up time was 27 months (range 18-35 months), and patients kept 98.6% of scheduled visits. After 6 months, the mean HbA1c in the intensive therapy group was at or below 7.3% and remained 2% lower than the standard group for the duration of the trial. Most of the decrease in the mean HbA1c in the intensive group was obtained by a single injection of evening intermediate insulin, alone or with daytime glipizide. By the end of the trial, 64% of the patients had advanced to two or more injections of insulin a day, aiming for normal HbA1c. However, only a small additional fall in HbA1c was attained. Severe hypoglycemia was rare (two events per 100 patients per year) and not significantly different between the groups, nor were changes in weight, blood pressure, or plasma lipids. There were 61 new cardiovascular events in 40 patients and 10 deaths (6 due to cardiovascular causes). CONCLUSIONS: Intense stepped insulin therapy in NIDDM patients who have failed glycemic control on pharmacological therapy is effective in maintaining near-normal glycemic control for > 2 years without excessive severe hypoglycemia, weight gain, hypertension, or dyslipidemia. Cardiovascular event rates are high at this stage of NIDDM. A long-term prospective trial is needed to assess the risk-benefit ratio of intensified treatment of hyperglycemia in NIDDM patients requiring insulin.

Safety and efficacy of normalizing fasting glucose with bedtime NPH insulin alone in NIDDM.

OBJECTIVE: To examine the safety and overall clinical effects of normalizing the fasting plasma glucose (FPG) level with bedtime NPH insulin alone in patients with non-insulin-dependent diabetes mellitus (NIDDM) that is poorly controlled with maximal doses of sulfonylureas. RESEARCH DESIGN AND METHODS: Twelve obese male NIDDM subjects were treated for 16 weeks with bedtime insulin after a 4-week sulfonylurea washout. The insulin dosage was increased until the FPG level was normalized. The 24-h plasma glucose profiles and lipid and HbA1c levels were measured at the beginning and end of the study, and the incidence and severity of hypoglycemic episodes were closely monitored. In addition, hyperglycemic clamp studies were performed to assess insulin secretion and provide an indirect measurement of insulin sensitivity. RESULTS: FPG (14.6 +/- 0.9 mmol/l at week 0) was normalized ( < 6.4 mmol/l) within 6 weeks (5.9 +/- 0.6 mmol/l) and remained at target levels until the end of the study (4.0 +/- 0.03 mmol/l at week 16, P < 0.001). The insulin dose was 80 +/- 9 U/day (0.86 +/- 0.10 U/kg). Improved glycemic control was confirmed by a reduction in HbA1c (10.9 +/- 0.05 vs. 7.2 +/- 0.2%, P < 0.001) and mean 24-h glucose (17.2 +/- 0.2 vs. 7.4 +/- 0.2 mmol/l, P < 0.001). The incidence of mild or moderate hypoglycemic episodes was 3.4 +/- 1/patient for the entire 16-week study, and no patient experienced severe hypoglycemia. Bedtime insulin significantly improved total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, and triglyceride levels (P < 0.01). Weight gain was 2.4 +/- 0.7 kg, and blood pressure was unchanged. During the hyperglycemic clamp, there was an improvement in the first phase (P < 0.001) and in the second phase (P < 0.01) of insulin secretion. There also was an increase in the rate of exogenous glucose infused (M) (P < 0.01) and in the M/C-peptide ratio (P < 0.02), suggesting enhanced insulin sensitivity. CONCLUSIONS: NPH insulin given at bedtime in amounts sufficient to achieve a normal FPG level does not cause excessive or severe hypoglycemia and does lead to good glycemic and lipid control in NIDDM. Bedtime insulin therapy also is accompanied by improved insulin secretion and insulin sensitivity. We conclude that a single dose of insulin alone at bedtime merits consideration as a therapeutic strategy in patients with poorly controlled NIDDM.

Do adipocytes contain high affinity sulfonylurea receptors.

Sulfonylureas interact with specific, high affinity receptors on the pancreatic beta-cell to close ATP-sensitive K+ channels, depolarize the cell, activate Ca2+ influx through voltage-dependent Ca2+ channels, and trigger insulin secretion. We tested the hypothesis that sulfonylureas promote glucose uptake into 3T3-L1 cells or isolated rat adipocytes by similar mechanisms. Using 125I-labeled 5-iodo-2-hydroxyglyburide and either equilibrium binding or photoaffinity labeling, a high affinity sulfonylurea receptor was not found on plasma membranes of either the 3T3-L1 cells or rat adipocytes. Furthermore, glyburide did not inhibit 86Rb+ efflux (a marker for ATP-sensitive K+ channel conductance), increase free cytosolic calcium in adipocytes or 3T3-L1 cells, or increase basal or insulin-stimulated glucose uptake into 3T3-L1 cells or rat adipocytes. Parallel studies using a hamster insulin-secreting tumor cell line (HIT cells) easily demonstrated both the receptor and biological effects of glyburide on free cytosolic calcium and insulin secretion. Thus, rat adipocytes and 3T3-L1 cells do not possess the high affinity sulfonylurea receptor or respond to glyburide alone. We conclude that the antidiabetogenic effects of sulfonylureas are not mediated by a direct action of sulfonylureas to increase glucose uptake into adipose tissue and suggest that the major locus for sulfonylurea action is the beta-cell.

Correlating genetic variation in carbon isotopic composition with complex climatic gradients.

Genetic variation in both carbon isotope discrimination and the proportions of leaf and photosynthetic twig tissues were observed in ecotypes of Hymenoclea salsola T.G., a common shrub in the deserts of the western United States, when grown under common garden conditions. These variations were correlated with climatic conditions in the habitats of origin through a model that described the leaf-to-air water vapor gradients experienced by plants during the growing season. Both carbon isotope discrimination and the proportion of leaves in the canopy were lower in plants derived from habitats with higher leaf-to-air vapor gradients, despite the fact that some of these sites received relatively high amounts of annual precipitation. These patterns were consistent with the notion that plants are able to maintain substantial control of water-use efficiency over large environmental gradients of temperature and moisture availability.

Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L.

In this paper we describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L. I. Gordon ([1965] in E Tongiorgi, ed, Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, Italy, pp 9-130) for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AWV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively depleted in heavy isotopes when exposed to AWV with a low heavy isotope composition, and leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate.

Protamine antibody production in diabetic subjects treated with NPH insulin.

Treatment with neutral protamine Hagedorn (NPH) insulin predisposes individuals with diabetes to anaphylactoid reactions when given bolus protamine for heparin reversal during cardiovascular procedures. To prospectively examine production of protamine antibodies, 30 patients with non-insulin dependent diabetes were followed for 12 months from initiation of therapy with porcine NPH or Lente insulin. Twenty-one subjects were randomly assigned to NPH (protamine containing) and nine controls to Lente (protamine free) insulin. Protamine specific IgG antibody was produced by 6/21 (29%) of NPH-treated subjects and 0/9 controls. Among NPH treated subjects, there was no difference between protamine antibody producers and non-producers with regard to age, race, weight, or pre-treatment glycosylated hemoglobin. Both producer and non-producer groups received similar amounts of insulin and protamine and achieved similar glycemic control. Insulin antibodies were made by 4/6 (67%) of protamine antibody producers and by 6/15 (40%) of non-producers (NS). The authors conclude that one of three new diabetics who are treated with porcine NPH insulin will make IgG protamine antibodies. These antibodies do not affect insulin requirements, glycemic control, or insulin antibody production. Because of the frequency of protamine antibody production and the risk of anaphylaxis to bolus protamine administration in NPH treated diabetics, the authors suggest that NPH insulin-treated individuals should avoid heparin reversal by protamine.

V.A. Cooperative Study of antiplatelet agents in diabetic patients after amputation for gangrene: unobserved, sudden, and unexpected deaths.

We report on unobserved, sudden, and unexpected deaths that occurred in a randomized multicenter trial. The long-term effects of aspirin plus dipyridamole on major vascular outcome variables were studied in 231 non insulin-dependent diabetic men with either a recent amputation for gangrene or active gangrene. Depending upon the definition of sudden death used, there were 14, 22, or 17 deaths in the drug group versus 6, 6, or 3 deaths in the placebo group (p = 0.04, 0.001, or 0.001, respectively). Total deaths from atherosclerotic vascular disease or deaths from all causes did not differ in the two treatment groups. Since this finding of a secondary end point is found only after multiple analyses of the data, it must be interpreted with caution. However, it is suggested that further studies on effects of antiplatelet agents on sudden deaths should be performed.