Rootstock Effects on Pistachio Trees Grown in Verticillium dahliae-Infested Soil

ABSTRACT In a field trial in soil infested with Verticillium dahliae, we compared the yield, growth, incidence of symptoms of Verticillium wilt, and mortality of two interspecific hybrid pistachio tree rootstocks (UCBI and PGII) with the standard rootstocks: the V. dahliae-resistant and susceptible Pistacia integerrima and P. atlantica, respectively. After 10 years, the trees were destructively sampled for V. dahliae in the xylem at the graft union. The results indicate that trees on the (P. atlantica 'KAC' x P. integerrima) hybrid UCBI rootstock grew and yielded as well as those on P. integerrima. Trees on the hybrid PGII yielded the least. Analysis of variance and log-linear models indicate that in soil infested with V. dahliae, three associations significantly affect pistachio nut yield. Rootstock affects scion vigor and extent of infection. Third, the extent of infection and scion vigor are inversely associated. Although trees on the P. integerrima rootstock had the highest ratings in a visual assessment of vigor, 65% were infected with V. dahliae in the trunk in the graft region compared with 73% in P. atlantica and 25% in UCBI. Thus, P. integerrima and UCBI have at least one different mechanism for resistance to V. dahliae.

The Australian Intervention Randomized Control of Rate in Atrial Fibrillation Trial (AIRCRAFT)

OBJECTIVES

The Australian Intervention Randomized Control of Rate in Atrial Fibrillation Trial was a multicenter trial of atrioventricular junction ablation and pacing (AVJAP) compared with pharmacologic ventricular rate control (medication [MED]) in patients with mild to moderately symptomatic permanent atrial fibrillation (AF).

BACKGROUND

There have been very few prospective randomized trials, undertaken in highly symptomatic patients, comparing AVJAP with pharmacologic methods of ventricular rate control for patients with permanent AF.

METHODS

There were 99 patients (70 men, mean age 68 +/- 8.6 years) at five centers. Forty-nine patients were randomized to AVJAP while 50 patients were randomized to pharmacologic control. The primary end point was cardiac function measured by echocardiography and exercise tolerance. The secondary end points were ventricular rate control, evaluated by 24-h ambulatory electrocardiographic monitoring, and quality of life. Data were collected at randomization and then at one month, six months, and 12 months post-randomization.

RESULTS

At 12 months follow-up there was no significant difference in left ventricular ejection fraction (AVJAP: 54 +/- 17%; MED: 61 +/- 13% [p = ns]) or exercise duration on treadmill testing (AVJAP: 4.1 +/- 2 min; MED: 4.6 +/- 2 min [p = ns]); however, the peak ventricular rate was lower in the AVJAP group during exercise (112 +/- 17 beats/min vs. 153 +/- 36 beats/min, p < 0.05) and activities of daily life (117 +/- 16 beats/min vs. 152 +/- 37 beats/min, p < 0.05). The CAST quality-of-life questionnaire revealed that patients in the AVJAP group had fewer symptoms at six months (p = 0.003) and at 12 months (p = 0.004). The observed relative risk reduction in symptoms at 12 months was 18%. Global subjective semiquantitative measurement of quality of life using the "ladder of life" revealed that the AVJAP group reported a 6% better quality of life at six months (p = 0.011).

CONCLUSIONS

In this trial, AVJAP for patients with mild to moderately symptomatic permanent AF did not worsen cardiac function during long-term follow-up, and quality of life was improved.

Ascaris suum, an intestinal parasite, produces morphine

The parasitic worm Ascaris suum contains the opiate alkaloid morphine as determined by HPLC coupled to electrochemical detection and by gas chromatography/mass spectrometry. The level of this material is 1168 +/- 278 ng/g worm wet weight. Furthermore, Ascaris maintained for 5 days contained a significant amount of morphine, as did their medium, demonstrating their ability to synthesize the opiate alkaloid. To determine whether the morphine was active, we exposed human monocytes to the material, and they immediately released nitric oxide in a naloxone-reversible manner. The anatomic distribution of morphine immunoreactivity reveals that the material is in the subcuticle layers and in the animals' nerve chords. Furthermore, as determined by RT-PCR, Ascaris does not express the transcript of the neuronal mu receptor. Failure to demonstrate the expression of this opioid receptor, as well as the morphine-like tissue localization in Ascaris, suggests that the endogenous morphine is intended for secretion into the microenvironment.

The potential to use PspA and other pneumococcal proteins to elicit protection against pneumococcal infection

Pneumococcal proteins, alone, in combination with each other, or in combination with capsular polysaccharide-protein conjugates may be useful pneumococcal vaccine components. Four proteins with a potential for use in vaccines are PspA, pneumolysin, PsaA, and PspC. In a mouse model of carriage, PsaA and PspC were the most efficacious vaccine proteins. Of these, PsaA was the best at eliciting protection against carriage. However, a combination of PspA and pneumolysin may elicit stronger immunity to pulmonary infection and possibly sepsis than either protein alone. Recently, a phase one trial of a recombinant family 1 PspA was completed in man. PspA was observed to be safe and immunogenic. Injection of 0.1 ml of immune serum diluted to 1/400 was able to protect mice from fatal infection with S. pneumoniae. Under these conditions, pre-immune serum was not protective. The immune human serum protected mice from infections with pneumococci expressing either of the major PspA families (1 and 2) and both of the pneumococcal capsular types tested: 3 and 6.

Early changes in biochemical markers of bone turnover predict the long-term response to alendronate therapy in representative elderly women: a randomized clinical trial

Although the antiresorptive agent alendronate has been shown to increase bone mineral density (BMD) at the hip and spine and decrease the incidence of osteoporotic fractures in older women, few data are available regarding early prediction of long-term response to therapy, particularly with regard to increases in hip BMD. Examining short-term changes in biochemical markers incorporates physiologic response with therapeutic compliance and should provide useful prognostic information for patients. The objective of this study was to examine whether early changes in biochemical markers of bone turnover predict long-term changes in hip BMD in elderly women. The study was a double-blind, placebo-controlled, randomized clinical trial which took place in a community-based academic hospital. One hundred and twenty community-dwelling, ambulatory women 65 years of age and older participated in the study. Intervention consisted of alendronate versus placebo for 2.5 years. All patients received appropriate calcium and vitamin D supplementation. The principal outcome measures included BMD of the hip (total hip, femoral neck, trochanter, and intertrochanter), spine (posteroanterior [PA] and lateral), total body, and radius. Biochemical markers of bone resorption included urinary N-telopeptide cross-linked collagen type I and free deoxypyridinoline; markers of bone formation included serum osteocalcin and bone-specific alkaline phosphatase. Long-term alendronate therapy was associated with increased BMD at the total hip (4.0%), femoral neck (3.1%), trochanter (5.5%), intertrochanter (3.8%), PA spine (7.8%), lateral spine (10.6%), total body (2.2%), and one-third distal radius (1.3%) in elderly women (all p < 0.01). In the placebo group, bone density increased 1.9-2.1% at the spine (p < 0.05) and remained stable at all other sites. At 6 months, there were significant decreases in all markers of bone turnover (-10% to -53%, p < 0.01) in women on alendronate. The changes in urinary cross-linked collagen at 6 months correlated with long-term bone density changes at the hip (r = -0.35, p < 0.01), trochanter (r = -0.36, p < 0.01), PA spine (r = -0.41, p < 0.01), and total body (r = -0.34, p < 0.05). At 6 months, patients with the greatest drop in urinary cross-linked collagen (65% or more) demonstrated the greatest gains in total hip, trochanteric, and vertebral bone density (all p < 0.05). A 30% decrease in urinary cross-linked collagen at 6 months predicted a bone density increase of 2.8-4.1% for the hip regions and 5.8-6.9% for the spine views at the 2.5-year time point (p < 0.05). There were no substantive associations between changes in biochemical markers and bone density in the placebo group. Alendronate therapy was associated with significant long-term gains in BMD at all clinically relevant sites, including the hip, in elderly women. Moreover, these improvements were associated with early decreases in biochemical markers of bone turnover. Early dynamic decreases in urinary cross-linked collagen can be used to monitor and predict long-term response to bisphosphonate therapy in elderly women. Future studies are needed to determine if early assessment improves long-term patient compliance or uncovers poor compliance, thereby aiding the physician in maximizing the benefits of therapy.

Randomized trial of pamidronate in patients with thyroid cancer: bone density is not reduced by suppressive doses of thyroxine, but is increased by cyclic intravenous pamidronate

Patients taking suppressive doses of T4 are thought to have accelerated bone loss and increased risk of osteoporosis. We therefore randomize 55 patients taking suppressive doses of T4 to treatment with pamidronate (APD) 30 mg i.v. every 3 months for 2 yr (APD/T4), or placebo (placebo/T4). Patients had measurements of bone mineral density (BMD) of the spine, hip, radius, and total body every 6 months for 2 yr. There was no significant bone loss at any site in the placebo/T4 group. Ninety five percent confidence intervals excluded a rate of bone loss > 0.89%/yr for the spine and > 0.31%/yr at the total hip. When men were excluded from the analysis, there still was no significant bone loss for the placebo/T4 group, and confidence intervals did not change. The APD/T4 group showed increases in spine (4.3%, P = 0.0001), total hip (1.4%, P < 0.05), and trochanteric (3.0%, P = 0.0001) BMDs. In conclusion, premenopausal women and men on suppressive therapy with T4 do not lose bone rapidly, and are not at increased risk of developing osteoporosis. A regimen of 30 mg APD given every 3 months for 2 yr causes significant suppression of bone resorption and increases in BMD, and may be an acceptable alternative treatment for osteoporosis in patients who cannot tolerate oral bisphosphonates.

Modulation of the potency of promutagens and direct acting mutagens in bacteria by inhibitors of the multidrug resistance mechanism

Multiple drug resistance (MDR) mechanisms are known to limit the effectiveness of some cancer chemotherapies, probably through enhancing P-glycoprotein-mediated drug efflux from mammalian cells. Similar mechanisms appear to act in other organisms, including bacteria, and may affect not only the toxicity but also the mutagenicity of certain chemicals. At least in some experimental situations, MDR can be overcome through concomitant treatment of the cells with various types of inhibitors. Two MDR inhibitors, verapamil, a calcium channel blocker, and trifluoperazine, a calmodulin inhibitor, were assayed for their ability to modulate the potency of nine mutagens with varying mechanisms of action in various Salmonella typhimurium his- strains. Neither verapamil nor trifluoperazine affected the direct mutagenicity of sodium dichromate and 2-methoxy-6-chloro-9[3-(2-chloroethyl)amino-propyl-amino] dihydrochloride (ICR 191) or the S9-mediated mutagenicity of benzo[a]pyrene and 2-amino-3,4-dimethyl-amidazo[4,5-f]quinoline (MeIQ). Both modulators enhanced the direct mutagenicity of doxorubicin. Moreover, trifluoperazine sharply increased the S9-mediated mutagenicity of cyclophosphamide and 2-aminofluorene, while it consistently decreased the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). The contrasting effect towards the aromatic amine 2-aminofluorene and the heterocyclic amine Trp-P-2, representative of important chemical families responsible for the bacterial mutagenicity of cigarette smoke, may explain the observed lack of influence of trifluoperazine on the mutagenicity of a cigarette smoke condensate. These observations extend the known range of chemical types whose mutagenicity can be modulated by inhibitors of MDR and suggest that there may be value in adding MDR inhibitors, especially trifluoperazine, to optimize the detection of mutagenicity by certain types of chemicals in the Salmonella/mammalian microsome mutagenicity test.

Efficacy of moxidectin, ivermectin and albendazole oral drenches for suppression of periparturient rise in ewe worm egg output and reduction of anthelmintic treatment for lambs

Sixty multiparous crossbred ewes which had lambed within three days in the first week of April 1996, were divided into four groups. Each group consisted of 15 ewes plus 12 pairs of twins and three single lambs. Group 1 was left untreated, group 2 was treated with albendazole 2.5 per cent drench, group 3 received moxidectin 0.1 per cent drench and group 4 received ivermectin 0.08 per cent drench. The ewes in each group were dosed with their anthelmintic on April 4 (day 0) before being turned out to separate equal-sized paddocks within the same field on the following morning. The field had been used for grazing sheep annually for many years and was considered to be contaminated with infective larvae of the common gastrointestinal nematodes infecting sheep in the region. Faecal samples were collected every two weeks from the ewes and lambs until July 25 (day 112). The lambs in each group were dosed with the anthelmintic used for their dams on day 42, and the dose was repeated when more than 50 per cent of the lambs in any group had a faecal egg count of more than 200 eggs per gram (epg). The total faecal egg output of the treated ewes over days 14 to 70, compared with that of the untreated control group, was reduced by 78.9 per cent by the moxidectin drench, by 47.6 per cent by ivermectin, and by 21.5 per cent by albendazole. The lambs in the groups treated with moxidectin and ivermectin required only one treatment on day 42 before reaching finishing weight; those in the albendazole-treated group were treated twice and the control group once. The faecal egg outputs of the lambs from day 42 until the end of the experiment on day 112 were reduced by 75 per cent by the moxidectin drench, by 48.5 per cent by ivermectin, and by 9 per cent by albendazole. There were no significant differences between the rates of weight change of either ewes or lambs in any of the groups.

Diurnal variation of bone mineral turnover in elderly men and women

The diurnal variation of markers of bone mineral metabolism have been documented in pre- and early postmenopausal women. Such rhythms have clinical implications for timing of sample collection and assessment of therapeutic intervention. To examine the diurnal variation of bone turnover in the elderly, we examined markers of bone formation [serum osteocalcin (OC) and bone-specific alkaline phosphatase (B-ALP)]; a marker of bone resorption (urinary N-telopeptide cross-linked collagen type 1 [NTX]); and serum calcium and parathyroid hormone (PTH) over 24 hours. Subjects were healthy community-dwelling elderly who were on no medications known to significantly alter bone mineral metabolism. Subjects included 14 women [74 +/- 6 years (mean +/- SD)] and 14 men (80 +/- 5 years). Over the 24-hour sampling period, mean serum OC, B-ALP, and calcium values were similar in elderly men and women. However, mean serum PTH was significantly higher in elderly men compared with women (P < 0.05). The magnitude of the diurnal variation of urinary NTX was significantly higher in women compared with men (P < 0.05). There was a significant diurnal variation for serum OC, B-ALP, calcium, PTH, and urinary NTX in both elderly men and women. The magnitude of the diurnal variation was approximately 10-20% of mean value for OC and B-ALP, 30% for PTH, and up to 40% for urinary NTX. We conclude that there is significant diurnal variation in the markers of bone mineral metabolism for elderly men and women. The peak value, which on average would be 20% higher than the mean value for urinary NTX, highlights the importance of the timing of sample collection for appropriate interpretation of therapeutic response. In addition, gender-related differences, including relatively higher levels of serum PTH and lower levels of urinary NTX in elderly men, may help explain differences in rates of bone loss in this age group.

Mechanisms and targets involved in maternal and paternal age effects on numerical aneuploidy

Trisomy in the human appears to be predominantly associated with maternal age. The maternal-age effect, however, shows considerable variability across affected chromosomes. Chromosome-specific variation has been reported in the shapes of the maternal-age-effect curves, including very small effects for the large chromosomes (groups A and B), linear increases (chromosome 16), and exponential increases (chromosome 21). There is also variation among chromosomes in whether the segregation errors occur predominantly at maternal meiosis I, meiosis II, and/or postfertilization mitotic divisions. There is also limited epidemiological evidence for a paternal-age effect, which was recently supported by the findings of age-related increases in sperm aneuploidy using fluorescence in situ hybridization methods. The paternal-age effect is considerably smaller than the maternal and is more likely to involve meiotic II errors of the sex chromosomes, whereas the maternal-age effect is more likely to arise from meiotic I errors producing autosomal trisomies. These and other differences suggest that constitutional aneuploidy arises by multiple mechanisms that may affect (1) the nature and timing of an initiating lesion affecting the oocyte or sperm; (2) the cellular physiology of the time of the nondisjunction event at meiosis I, II, or postfertilization; and (3) the selection against specific chromosomal aneuploidies during embryonic development. Multidisciplinary research is needed to understand the maternal and paternal-age effects on aneuploidy, to (1) identify and characterize the genes that control meiosis, recombination, and segregation; (2) identify the micro-environmental factors around the oocyte and mole germ cells that are involved in the age effects; (3) develop a laboratory animal model for the age effects; (4) characterize the role of genetics, physiology, and environmental toxicology for the paternal-age effects; and (5) identify cohorts of men and women of differing ages who have been exposed to high doses of candidate aneugens and conduct epidemiological investigations of aneuploidies transmitted to their offspring.

Casemix issues for nursing

The diagnosis-related groups (DRGs) patient classification system provides information about the type and volume of acute inpatients treated, as well as the length of stay and cost of treatment. Nurses have been involved in casemix development in Australia, providing advice to government departments on nursing issues; researching the relative cost of nursing patients in one diagnosis-related group compared with another; budgeting nursing resources for casemix treated; and using casemix information to change practices to achieve more efficient use of resources and maintain quality of care. Casemix information allows nurses to contribute to the management of clinical services in partnership with other clinicians and managers.

The use of non-denaturing Deriphat-polyacrylamide gel electrophoresis to fractionate pigment-protein complexes of purple bacteria

The suitability of Deriphat-polyacrylamide gel electrophoresis as a method for separating purple bacterial pigment-protein complexes has been tested. When appropriate non-denaturing detergents are used to solubilize chromatophores, this method provides a rapid, easy and microscale procedure for analyzing the composition of the bacterial photosynthetic apparatus with minimal disruption of individual pigment-proteins. Its usefulness is further illustrated by employing it to test for suitable detergents with which to solubilize purple bacterial chromatophores, and as an assay to study variation in the composition of the photosynthetic unit of bacterial cultures grown under different conditions.

Subarachnoid hemorrhage in sickle-cell disease

The neurological complications of sickle-cell disease include cerebral intracerebral hemorrhage; subarachnoid hemorrhage (SAH) has been infrequently reported. Among 325 patients with sickle-cell disease followed at the University of Illinois between 1975 and 1989, 11 cases of SAH were identified. Aneurysms were found in 10 of these patients, three of whom had multiple aneurysms. All of the patients had some degree of anemia and nine underwent craniotomy without hematological or neurological complications. From this review it appears that SAH is not uncommon in sickle-cell disease patients and tends to occur at a younger age and with smaller aneurysm size than in the general population. With proper perioperative management, including exchange transfusions to reduce the proportion of hemoglobin S to less than 30%, these patients can undergo angiography and craniotomy without an increased incidence of complications. The techniques used in managing sickle-cell disease patients with SAH are discussed.

Intracarotid saline infusion improves outcome from incomplete ischemia in rats

Previous studies suggest that rheological changes associated with ischemia may produce postischemic hypoperfusion. We tested whether intracarotid or intravenous infusions of saline improve neurological outcome from incomplete cerebral ischemia in rats. Rats were anesthetized with 1.4% isoflurane in air, and ischemia was produced by unilateral carotid artery ligation combined with hemorrhagic hypotension to 30 mm Hg for 30 minutes. Intracarotid (n = 10) or intravenous (n = 10) saline infusion (0.3 ml/min) decreased hematocrit 20% compared with control rats (n = 10). Neurological outcome was significantly improved in rats infused with intracarotid (p less than 0.05) but not intravenous saline during ischemia without a change in brain temperature. Cerebral blood flow, measured in a separate study using laser Doppler flowmetry (n = 5), decreased 70% (p less than 0.01) during carotid ligation and hypotension but was not changed by intracarotid saline infusion (p greater than 0.30). These results show that perfusion of ischemic brain with saline improves outcome by factors not related to changes in hematocrit, brain temperature, or intraischemic tissue blood flow.

American Express emphasizes service, training and R&D. Interview by Carolyn Dunbar

Larry Ferguson, president of the Health Systems Group of American Express Information Services Company, tells Computers in Healthcare what has happened in the year since the company acquired enough "critical mass" through purchasing McDonnell Douglas Health Systems Company to become a major player in the healthcare computing industry.

"Instant-mix" whole brain photon with neutron boost radiotherapy for malignant gliomas

From July 1985 through March 1987, 44 consecutive patients with supratentorial, nonmetastatic anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM) were treated with whole brain photon irradiation with concomitant neutron boost at the University of Chicago. All patients had biopsy proven disease and surgery ranged from biopsy to total gross excision. Whole brain photon radiation was given at 1.5 Gy per fraction, 5 days weekly for a total dose of 45 Gy in 6 weeks. Neutron boost radiation was prescribed to a target minimum dose that included the pre-surgical CT tumor volume plus 1 cm margin. Neutrons were administered 5-20 minutes prior to photon radiation twice weekly and a total dose of 5.2 Gyn gamma was administered over 6 weeks. Median follow-up was 36 months. The median survival was 40.3 months for anaplastic astrocytoma (10 patients) and 11 months for glioblastoma multiforme (34 patients) and 12 months for the overall group. Variables that predicted longer median survival included histology (AA vs. GBM), age (less than or equal to 39 years vs. older), and extent of surgery (total gross or partial excision vs. biopsy) whereas tumor size and Karnofsky performance status did not have a significant influence. The median survival of the anaplastic astrocytoma group was better than expected compared to the RTOG 80-07 study (a dose-finding study of similar design to this study) and historical data. Reasons for this are discussed.

Unique use of a tip-deflecting guide wire in removing a catheter embolus from an infant

An umbilical catheter fragment embolus in a neonate was difficult to approach due to fixation of both ends, in the left atrial appendage and the ductus venosus, respectively. A tip-deflecting guide wire was used in unique fashion to free the catheter fragment and allow its percutaneous removal via the femoral vein approach.

The significance of tibial artery disease in the management of popliteal aneurysms

The clinical, radiographic and histologic features of sixty-one popliteal aneurysms in 36 patients are reviewed. Twenty-seven aneurysms were thrombosed and presented with an acutely ischaemic limb or the sudden onset of severe claudication. Thirty-four patent aneurysms presented with either ischaemic ulceration or claudication due to tibial artery disease or were asymptomatic with normal distal pulses. Thrombosis made reconstruction difficult and at times required a femoro-tibial graft. In others reconstruction was not possible leading to amputation either as primary treatment or following failed revascularization. In patent aneurysms one or more tibial arteries were frequently occluded. It is postulated that obliterative atheromatous disease of the tibial vessels and the slow flow through the aneurysmal vessels is responsible for the high incidence of thrombosis, poor graft patency and a high amputation rate.

Incidence of the radial steal syndrome in patients with Brescia fistula for hemodialysis: its clinical significance

The Brescia fistula is the method of choice for providing vascular access in patients who have chronic kidney failure that requires hemodialysis. This study investigated hand hemodynamics in patients with Brescia fistulas to determine the incidence of radial steal and its relationship to symptoms of arterial insufficiency of the hand. Twenty-three patients, one of whom had symptoms of arterial insufficiency, were studied. Thumb systolic blood pressure was determined by photoplethysmography under resting conditions and with the fistula, radial, and ulnar arteries occluded successively by digital pressure. The brachial pressure was determined by Doppler ultrasonography and the thumb/arm pressure ratio was determined for each experimental condition. The presence of a Brescia fistula resulted in a 40% reduction of the thumb blood pressure (median thumb/arm ratio = 0.61), which returned to normal (median ratio = 1.03) when the fistula was occluded. Occlusion of the radial artery distal to the fistula resulted in a significant increase in thumb blood pressure (median ratio = 0.89; p less than 0.001), indicating the presence of radial steal. This phenomenon occurred in 21 of the 24 fistulas (88%) studied. This study demonstrated that the radial steal phenomenon occurs in most patients with Brescia fistulas but in only a small number of these patients do symptoms of arterial insufficiency develop.

Interposition vein cuff for anastomosis of prosthesis to small artery

This paper reports the use of a vein cuff to facilitate the anastomosis of a prosthetic graft to a small artery. This technique makes it easier to perform a good anastomosis and may improve the chances of long-term patency.

Mechanisms of the fasting-induced dissociation of insulin binding from its action in isolated rat hepatocytes

Fasting leads to an increase in insulin binding to isolated rat hepatocytes from 12 to 17%. This increase was accounted for by changes in the affinity of insulin receptors without alteration in their number. In contrast, the responsiveness of hepatocytes to insulin was markedly diminished in fasted rats. Both basal and insulin-stimulated rates of 14C-glucose incorporation into glycogen were significantly decreased in fasted animals. When insulin-induced 14C-glucose incorporation into glycogen was expressed as a percent above the basal rate, hepatocytes isolated both from control and fasted animals showed the same magnitude of maximal response (66 +/- 13% in fed and 59 +/- 12% in fasted animals, respectively). However, more insulin must be bound to hepatocytes isolated from fasted animals in order to elicit the same percent of insulin's maximal effect. Incubation of 'fed' hepatocytes in the serum obtained from fasted rats significantly diminished their responsiveness to insulin. An addition of insulin (100 ng/ml), glucose (10 mM) and antibodies to glucagon (1:100) eliminated the inhibitory effect of 'fasted' serum on 'fed' hepatocytes. A 48-hour fast increased significantly the microviscosity (decreased fluidity) of hepatocyte plasma membranes and altered membrane phospholipid composition. These changes correlated with enhanced insulin binding to isolated membranes. Moreover, in response to insulin, plasma membranes isolated from 'fasted' hepatocytes generated only one half the amount of the second messenger (PDH activator) observed in membranes of fed animals. The amount of PDH activator generated by incubation of plasma membranes with insulin correlated inversely with both insulin binding and membrane microviscosity. We conclude that 1) fasting induces both coupling defect and post-receptor changes in insulin's action; 2) both extracellular and intracellular factors contribute to fasting-induced dissociation of insulin binding from insulin action; 3) insulin/glucagon ratio may influence hepatocyte responsiveness to insulin; 4) alterations in plasma membrane fluidity and phospholipid composition may alter insulin binding and contribute to its dissociation from the subsequent action; 5) membranes isolated from 'fasted' hepatocytes generate less mediator of insulin action than do membranes isolated from 'fed' hepatocytes.

Quantitative studies of the rate of insulin internalization in isolated rat hepatocytes

We studied internalization of 125I-labelled insulin in isolated rat hepatocytes. Using the acidification technique, we were able to dissociate the ligand from its cell-surface receptors, and thus to separate internalized from surface-bound insulin. Because during the first 5 min of incubation of 125I-labelled insulin with freshly isolated hepatocytes there is no loss of internalized label, the ratio of the amount of internalized ligand to the amount of cell-surface-bound ligand may serve as an index of insulin internalization. Within the first 10 min of insulin's interaction with hepatocytes, the plot of the above ratio as a function of time yields a straight line. The slope of this line is referred to as the endocytic rate constant (Ke) for insulin and denotes the probability with which the insulin-receptor complex is internalized in 1 min. At the insulin concentration of 0.295 ng/ml, the Ke is 0.049 min-1. It is independent of insulin concentration until the latter exceeds 1 ng/ml. At the insulin concentration of 3.2 ng/ml, the Ke accelerates to 0.131 min-1. With the Ke being the probability of insulin-receptor-complex internalization, 4.9% of occupied insulin receptors will be internalized in 1 min at an insulin concentration of 0.295 ng/ml, and 13.1% of occupied insulin receptors will be internalized in 1 min at 3.2 ng/ml. When the insulin concentration decreases from 3.2 to 0.3 ng/ml, the Ke decreases accordingly. The half-time of occupied receptor internalization is 15.4 min at the lower insulin concentration and 5.3 min at the higher insulin concentration.

Determination of the ligand-binding characteristics of several tight-binding mutants of the lactose repressor protein

Several tight-binding mutants of the lactose repressor protein have been characterized with respect to their fluorescence properties and their inducer, operator and nonspecific DNA-binding constants. The tryptophan fluorescence emission spectra for the mutants and the wild-type repressor are quite similar. However, alterations in the Stern-Volmer constants for iodide quenching of the tryptophans in the mutant proteins compared to wild-type suggest differences in the local environment or solvent accessibility for these amino acids in the tight-binding repressors. The inducer-binding affinities and association rate constants of the mutant proteins and protein-operator DNA fragment complexes are also altered compared to wild-type. The extents of these changes vary among the different mutant repressors. The nonspecific DNA-binding affinities of the mutant proteins are 2--3-fold greater than the wild-type repressor, and the affinities of the tight-binding proteins for a 29 base-pair operator DNA fragment are also increased, though to a varying extent depending upon the mutant. The phenotypic behavior of these proteins in vivo can be partially explained by these results obtained in vitro; however, it is likely that there are additional factors responsible for the tight-binding behavior of the proteins that were not detectable in these experiments.

Eosinophilic granuloma of the second cervical vertebra

The occurrence of eosinophilic granuloma in the body of the second cervical vertebra of a young adult male is presented. The necessity of making a histologic diagnosis and prevention of vertebral instability led to operative intervention. Treatment consisted of posterior fixation of the spinous processes of the second and third cervical vertebrae with size 0 wire. Through a transoral approach the lesion was curetted, and bone chips were placed in the vertebral defect. The patient remains well, and disease-free, after 36 months.