Prestin is the motor protein of cochlear outer hair cells

The outer and inner hair cells of the mammalian cochlea perform different functions. In response to changes in membrane potential, the cylindrical outer hair cell rapidly alters its length and stiffness. These mechanical changes, driven by putative molecular motors, are assumed to produce amplification of vibrations in the cochlea that are transduced by inner hair cells. Here we have identified an abundant complementary DNA from a gene, designated Prestin, which is specifically expressed in outer hair cells. Regions of the encoded protein show moderate sequence similarity to pendrin and related sulphate/anion transport proteins. Voltage-induced shape changes can be elicited in cultured human kidney cells that express prestin. The mechanical response of outer hair cells to voltage change is accompanied by a 'gating current', which is manifested as nonlinear capacitance. We also demonstrate this nonlinear capacitance in transfected kidney cells. We conclude that prestin is the motor protein of the cochlear outer hair cell.

Signal transduction cascades regulating fungal development and virulence

Cellular differentiation, mating, and filamentous growth are regulated in many fungi by environmental and nutritional signals. For example, in response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous growth referred to as pseudohyphal differentiation. Yeast filamentous growth is regulated, in part, by two conserved signal transduction cascades: a mitogen-activated protein kinase cascade and a G-protein regulated cyclic AMP signaling pathway. Related signaling cascades play an analogous role in regulating mating and virulence in the plant fungal pathogen Ustilago maydis and the human fungal pathogens Cryptococcus neoformans and Candida albicans. We review here studies on the signaling cascades that regulate development of these and other fungi. This analysis illustrates both how the model yeast S. cerevisiae can serve as a paradigm for signaling in other organisms and also how studies in other fungi provide insights into conserved signaling pathways that operate in many divergent organisms.

Regulation of vascular endothelial growth factor-dependent retinal neovascularization by insulin-like growth factor-1 receptor

Although insulin-like growth factor 1 (IGF-1) has been associated with retinopathy, proof of a direct relationship has been lacking. Here we show that an IGF-1 receptor antagonist suppresses retinal neovascularization in vivo, and infer that interactions between IGF-1 and the IGF-1 receptor are necessary for induction of maximal neovascularization by vascular endothelial growth factor (VEGF). IGF-1 receptor regulation of VEGF action is mediated at least in part through control of VEGF activation of p44/42 mitogen-activated protein kinase, establishing a hierarchical relationship between IGF-1 and VEGF receptors. These findings establish an essential role for IGF-1 in angiogenesis and demonstrate a new target for control of retinopathy. They also explain why diabetic retinopathy initially increases with the onset of insulin treatment. IGF-1 levels, low in untreated diabetes, rise with insulin therapy, permitting VEGF-induced retinopathy.

A seven-transmembrane, G protein-coupled receptor, FPRL1, mediates the chemotactic activity of serum amyloid A for human phagocytic cells

We have previously reported (Badolato, R., J.M. Wang, W.J. Murphy, A. R. Lloyd, D.F. Michiel, L.L. Bausserman, D.J. Kelvin, and J.J. Oppenheim. 1994. J. Exp. Med. 180:203; Xu, L., R. Badolato, W.J. Murphy, D.L. Longo, M. Anver, S. Hale, J.J. Oppenheim, and J.M. Wang. 1995. J. Immunol. 155:1184.) that the acute phase protein serum amyloid A (SAA) is a potent chemoattractant for human leukocytes in vitro and mouse phagocytes in vivo. To identify the signaling mechanisms, we evaluated patterns of cross-desensitization between SAA and other leukocyte chemoattractants. We found that the chemotactic bacterial peptide, N-formyl- methionyl-leucyl-phenylalanine (fMLP), was able to specifically attenuate Ca2+ mobilization in human phagocytes induced by SAA, but only at very high concentrations, suggesting that SAA uses a low affinity fMLP receptor. Here we demonstrate that SAA selectively induced Ca2+ mobilization and migration of HEK cells expressing FPRL1, a human seven-transmembrane domain phagocyte receptor with low affinity for fMLP, and high affinity for lipoxin A4. Furthermore, radiolabeled SAA specifically bound to human phagocytes and FPRL1-transfected 293 cells. In contrast, SAA was not a ligand or agonist for FPR, the high affinity fMLP receptor. Thus, SAA is the first chemotactic ligand identified for FPRL1. Our results suggest that FPRL1 mediates phagocyte migration in response to SAA.

Health-related quality of life in postmenopausal women with low BMD with or without prevalent vertebral fractures

Fractures and subsequent morbidity determine the impact of established postmenopausal osteoporosis. Health-related quality of life (HRQOL) has become an important outcome criterion in the assessment and follow-up of osteoporotic patients. As part of the baseline measurements of the Multiple Outcomes of Raloxifene Evaluation (MORE) study, HRQOL was assessed in 751 osteoporotic (bone mineral density [BMD] T score > or = -2.5) women from Europe with or without vertebral fractures (VFX). This was done using the quality of life questionnaire of the European Foundation for Osteoporosis (QUALEFFO), Nottingham Health Profile (NHP) and the EQ-5D (former EuroQol). QUALEFFO contains questions in five domains: pain, physical function, social function, general health perception, and mental function. Each domain score and QUALEFFO total scores are expressed on a 100-point scale, with 0 corresponding to the best HRQOL. In comparison with patients without VFX, those with VFX were older (66.2 +/- 5.9 years vs. 68.8 +/- 6.3 years; p < 0.001), had higher prevalence of nonvertebral fractures (25% vs. 36%; p = 0.002), and higher QUALEFFO scores (worse HRQOL; total score, 26 +/- 14 vs. 36 +/- 17; p < 0.001). QUALEFFO scores increased progressively with increasing number of VFX, especially lumbar fractures (p < 0.001). Patients with a single VFX already had a significant increase in QUALEFFO scores (p < 0.05). Similar, though weaker, associations were seen for NHP and EQ-5D scores. This study confirms decreased HRQOL for patients with prevalent VFX. In osteoporotic patients, QUALEFFO scores change in relation to the number of VFX. QUALEFFO is suitable for clinical studies in patients with postmenopausal osteoporosis.

Redundant roles for the TFIID and SAGA complexes in global transcription

The transcription factors TFIID and SAGA are multi-subunit complexes involved in transcription by RNA polymerase II. TFIID and SAGA contain common TATA-binding protein (TBP)-associated factor (TAF(II)) subunits and each complex contains a subunit with histone acetyltransferase activity. These observations have raised questions about whether the functions of the two complexes in vivo are unique or overlapping. Here we use genome-wide expression analysis to investigate how expression of the yeast genome depends on both shared and unique subunits of these two complexes. We find that expression of most genes requires one or more of the common TAF(II) subunits, indicating that the functions of TFIID and SAGA are widely required for gene expression. Among the subunits shared by TFIID and SAGA are three histone-like TAF(II)s, which have been proposed to form a sub-complex and mediate a common function in global transcription. Unexpectedly, we find that the histone-like TAF(II)s have distinct roles in expression of the yeast genome. Most importantly, we show that the histone acetylase components of TFIID and SAGA (TAF(II)145 and Gcn5) are functionally redundant, indicating that expression of a large fraction of yeast genes can be regulated through the action of either complex.

The relationship of health-related quality of life to prevalent and incident vertebral fractures in postmenopausal women with osteoporosis: results from the Multiple Outcomes of Raloxifene Evaluation Study

OBJECTIVE

To examine the effect of both prevalent and incident vertebral fractures on health-related quality of life (HRQOL) in postmenopausal women with osteoporosis and to characterize the effect of prevalent vertebral fractures on HRQOL with respect to number, location, severity, and adjacency.

METHODS

Participants were a subset of women (n = 1,395, mean age 68.5 years) from the Multiple Outcomes of Raloxifene Evaluation trial who had low bone mineral density and/or prevalent vertebral fractures. Vertebral fractures were measured by radiography at baseline, 2 years, and 3 years. HRQOL was assessed using the Osteoporosis Assessment Questionnaire (OPAQ), a validated disease-targeted instrument, at baseline and annually for 3 years.

RESULTS

Both prevalent and incident radiographic vertebral fractures were associated with decreased HRQOL. At baseline, women with a prevalent vertebral fracture had significantly lower OPAQ scores on physical function, emotional status, clinical symptoms, and overall HRQOL compared with women without a prevalent fracture (all P < 0.01). HRQOL scores were lower with each subsequent fracture. The effect of prevalent vertebral fracture was dependent on the location within the spine and was strongest in the lumbar region (L1-L4). Incident vertebral fractures significantly decreased OPAQ scores on physical function, emotional status, clinical symptoms, and overall HRQOL (all P < 0.001).

CONCLUSION

Our findings demonstrate the importance of treating postmenopausal women who have prevalent vertebral fractures to prevent further decreases in HRQOL associated with subsequent incident vertebral fracture.

Role of nitric oxide in the regulation of oxygen consumption in conscious dogs

The role of nitric oxide (NO) in the regulation of O2 consumption was studied in chronically instrumented conscious dogs. A specific NO synthesis inhibitor, nitro-L-arginine (NLA, 30 mg/kg i.v.), significantly increased mean arterial pressure from 100 +/- 4 to 134 +/- 5 mm Hg (mean +/- SEM) and total peripheral resistance by 157 +/- 16% and reduced cardiac output by 47 +/- 3% and heart rate by 34 +/- 6% after 120 minutes. Changes in arterial blood gases were not observed. There were significant changes in PO2 (-14 +/- 2 mm Hg), O2 saturation (-21 +/- 2%), the percentage of hemoglobin as oxyhemoglobin (-21 +/- 2%), and O2 content (-3.0 +/- 0.9 vol%) and a significant increase in percent reduced hemoglobin (21 +/- 1%) in mixed venous blood, associated with an increase in O2 extraction (5.1 +/- 0.2 vol%) (all P < .01). O2 consumption was increased from 124 +/- 6 to 155 +/- 9 mL/min (P < .05). Methoxamine, titrated to have hemodynamic effects similar to those of NLA (eg, mean arterial pressure increased from 97 +/- 4 to 131 +/- 5 mm Hg), had much smaller effects on venous blood gases, hemoglobin, and O2 extraction (2.3 +/- 0.7 vol%) and no significant effect on O2 consumption. NLA also caused an increase in O2 consumption of 37 +/- 8% (P < .01) in quietly resting conscious dogs that had undergone pretreatment with hexamethonium and atropine, but no significant change in O2 consumption in dogs anesthetized with barbiturate.(ABSTRACT TRUNCATED AT 250 WORDS)

Ectopic eye development in Drosophila induced by directed dachshund expression

The dachshund gene encodes a nuclear protein that is required for normal eye development in Drosophila. In the absence of dachshund function, flies develop with severely reduced or no eyes. We show that targeted expression of dachshund is sufficient to direct ectopic retinal development in a variety of tissues, including the adult head, thorax and legs. This result is similar to that observed with the highly conserved Drosophila gene eyeless, which can induce ectopic eye formation on all major appendages. Here, we show that dachshund and eyeless induce the expression of each other and that dachshund is required for ectopic retinal development driven by eyeless misexpression. These results suggest that the control of eye development requires the complex interaction of multiple genes, even at the very highest regulatory levels.

MRI-measured bone marrow adipose tissue is inversely related to DXA-measured bone mineral in Caucasian women

INTRODUCTION

Recent studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Previous research using regional magnetic resonance spectroscopy methods to measure BMAT has reported inconsistent findings on the relationship between BMAT and dual-energy absorptiometry (DXA)-measured bone mineral density (BMD).

METHODS

In the present study, total body and pelvic BMAT were evaluated in 56 healthy women (age 18-88 yrs, mean +/- SD, 47.4 +/- 17.6 yrs; BMI, 24.3 +/- 4.2 kg/m(2)) with T1-weighted whole-body magnetic resonance imaging (MRI). BMD was measured using the whole-body DXA mode (GE Lunar DPX, software version 4.7).

RESULTS

A strong negative correlation was observed between pelvic BMAT and BMD (total-body BMD, R = -0.743, P < 0.001; pelvic BMD, R = -0.646, P < 0.001), and between total-body BMAT and BMD (total-body BMD, R = -0.443, P < 0.001; pelvic BMD, R = -0.308, P < 0.001). The inverse association between pelvic BMAT and BMD remained strong after adjusting for age, weight, total body fat, and menopausal status (partial correlation: total-body BMD, R = -0.553, P < 0.001; pelvic BMD, R = -0.513, P < 0.001). BMAT was also highly correlated with age (pelvic BMAT, R = 0.715, P < 0.001; total-body BMAT, R = 0.519, P < 0.001).

CONCLUSION

MRI-measured BMAT is thus strongly inversely correlated with DXA-measured BMD independent of other predictor variables. These observations, in the context of DXA technical concerns, support the growing evidence linking BMAT with low bone density.

Weight loss composition is one-fourth fat-free mass: a critical review and critique of this widely cited rule

Maximizing fat loss while preserving lean tissue mass and function is a central goal of modern obesity treatments. A widely cited rule guiding expected loss of lean tissue as fat-free mass (FFM) states that approximately one-fourth of weight loss will be FFM (i.e. ΔFFM/ΔWeight = ∼0.25), with the remaining three-fourths being fat mass. This review examines the dynamic relationships between FFM, fat mass and weight changes that follow induction of negative energy balance with hypocaloric dieting and/or exercise. Historical developments in the field are traced with the 'Quarter FFM Rule' used as a framework to examine evolving concepts on obesity tissue, excess weight and what is often cited as 'Forbes' Rule'. Temporal effects in the fractional contribution of FFM to changes in body weight are examined as are lean tissue moderating effects such as ageing, inactivity and exercise that frequently accompany structured low-calorie diet weight loss protocols. Losses of lean tissue with dieting typically tend to be small, raising questions about study design, power and applied measurement method reliability. Our review elicits important questions related to the fractional loss of lean tissues with dieting and provides a foundation for future research on this topic.

Yeast TAF(II)145 functions as a core promoter selectivity factor, not a general coactivator

In yeast, TATA box binding protein associated factors (TAF(II)s) are dispensable for transcription of most genes. Here we use differential display to identify a small subset of yeast genes whose transcription in vivo requires yTAF(II)145. Promoter-mapping studies reveal, unexpectedly, that the region of a gene that renders it yTAF(II)145-dependent is not the upstream activating sequence, which contains the activator-binding sites, but rather the core promoter. In fact, a core promoter requiring yTAF(II)145 retained that requirement when its transcription was directed by several unrelated upstream activating sequences and even in the absence of an activator. Taken together, our results indicate that yTAF(II)145 functions in recognition and selection of core promoters by a mechanism not involving upstream activators.

Nitric oxide. An important signaling mechanism between vascular endothelium and parenchymal cells in the regulation of oxygen consumption

BACKGROUND

Nitric oxide (NO) is known to be an inhibitor of mitochondrial function. However, the physiological significance of endothelium-derived NO in the control of tissue respiration is not established.

METHODS AND RESULTS

Tissue O2 consumption by skeletal muscle slices of the triceps brachii of normal dogs was measured with a Clark-type O2 electrode/tissue bath system at 37 degrees C. S-Nitroso-N-acetylpenicillamine (SNAP), carbachol (CCh), or bradykinin (BK) decreased tissue O2 consumption by 12 +/- 3% to 55 +/- 8%, 15 +/- 6% to 36 +/- 11%, or 21 +/- 5% to 42 +/- 4% at doses of 10(-7) to 10(-4) mol/L, respectively. The effects of both CCh and BK but not SNAP were eliminated by nitro-L-arginine (NLA, 10(-4) mol/L), consistent with SNAP decomposing to release NO and both CCh and BK stimulating endogenous NO production from L-arginine. Oxygen consumption was also decreased by 8-bromo-cGMP. The mitochondrial uncoupler dinitrophenol blocked the effects of 8-bromo-cGMP but only slightly altered those of SNAP, indicating that the major site of action of NO is the mitochondria. In normal, chronically instrumented, resting conscious dogs, blockade of NO synthase by NLA increased mean arterial pressure by 28 +/- 2.5 mm Hg and hind limb vascular resistance by 114 +/- 12% and decreased blood flow by 39 +/- 3%. Most important, NLA also increased O2 uptake by 55 +/- 9% in hind limb skeletal muscle (P < .05), associated with decreases in PO2 and O2 saturation and an increase in reduced hemoglobin in hind limb venous blood.

CONCLUSIONS

Our results indicate that NO release from vascular endothelial cells appears to play an important physiological role in the regulation of tissue mitochondrial respiration in skeletal muscle and perhaps other organ systems.

Presenting the diagnosis of pseudoseizure

Simultaneous video-EEG monitoring has allowed pseudoseizures to be effectively diagnosed. Discussing the results of the monitoring with the patient is the 1st step in treatment. We outline a protocol for presenting the diagnosis of pseudoseizure with the goal of conveying to the patient the importance of knowing the nonepileptic nature of the spells and the need for psychiatric follow-up. The protocol also allows elicitation of sexual abuse history and the use of suggestion to aid in controlling the pseudoseizures.

Pharmacodynamics of plasma nitrate/nitrite as an indication of nitric oxide formation in conscious dogs

BACKGROUND

The present investigation was undertaken to better understand the production of nitric oxide (NO) in vivo as measured by alterations in plasma nitrite or nitrate in blood samples from studies in experimental animals or clinical studies in humans.

METHODS AND RESULTS

Plasma samples were taken from the aorta, the coronary sinus, a peripheral vein in the leg (skeletal muscle), or the right ventricle (mixed venous) in chronically instrumented conscious dogs. Plasma nitrite was converted to NO gas in an argon environment by use of hydrochloric acid, and plasma nitrate was converted first to nitrite with nitrate reductase and then to NO gas with acid. Standard curves were constructed, and the amount of nitrite and nitrate in plasma was determined. The primary metabolite was nitrate, whereas nitrate was approximately 10% of the total and remained constant. In the resting dog, the only vascular bed with a positive arterial-venous nitrate difference, evidence for production of NO, was the heart. Nitrate infusion into quietly resting dogs resulted in increases in plasma nitrate up to 38 +/- 3.4 mmol/L, increases in systemic arterial pressure, and a marked diuresis. The plasma half-life was calculated as 3.8 hours. The volume of distribution was calculated as 0.215 L/kg, or equivalent to the extracellular volume.

CONCLUSIONS

These studies indicate that nitrate is a reliable measure of NO metabolism in vivo but that because of the long half-life, nitrate will accumulate in plasma once it is produced. Because of the large volume of distribution (21% of body weight versus the 4% of body weight usually attributed to plasma volume, the compartment in which nitrate is measured), simple measures of plasma nitrate underestimate by a factor of 4 to 6 the actual production of nitrate or NO by the body. In disease states, such as heart failure, in which renal function and extracellular volume are altered, caution should be exercised when increases in nitrate in plasma as an index of NO formation are evaluated.

The efficacy and safety of tadalafil: an update

OBJECTIVE

To provide an update on the efficacy and safety of tadalafil, a phosphodiesterase-5 inhibitor, in the treatment of erectile dysfunction (ED).

PATIENTS AND METHODS

In all, 2102 men (mean age 56 years) with mild-to-severe ED of various causes were randomized to placebo or tadalafil, taken as needed with no food restrictions, at fixed 'on-demand' doses of 10 or 20 mg in 11 randomized, double-blind, placebo-controlled trials lasting 12 weeks. The three co-primary outcomes were changes from baseline in the erectile function domain of the International Index of Erectile Function (IIEF) and the proportion of 'yes' responses to questions 2 and 3 of the Sexual Encounter Profile (SEP). Additional efficacy instruments included a Global Assessment Question (GAQ).

RESULTS

Compared with placebo, tadalafil gave significantly better outcomes. Patients receiving either dose of tadalafil had a significant mean improvement of 6.5 and 8.6, respectively, in the IIEF erectile function domain score from baseline (P < 0.001 vs placebo). At both doses the mean success rate for intercourse attempts (SEP-Q3) was 58% and 68%, respectively, compared with 31% in the placebo group (P < 0.001), and 71% and 84% reported improved erections at the endpoint (GAQ), vs 33% on placebo (P < 0.001). Tadalafil was effective up to 36 h after dosing and was effective regardless of disease severity and causes, and in patients of all ages. The most frequent adverse events were headache, dyspepsia, back pain and myalgia.

CONCLUSION

Tadalafil was an effective and well-tolerated treatment for ED.

Role of endothelium-derived nitric oxide in the modulation of canine myocardial mitochondrial respiration in vitro. Implications for the development of heart failure

The mechanism responsible for the regulation of cardiac function by endogenous nitric oxide (NO) remains unclear. In this investigation, O2 consumption by freshly isolated myocardial muscle segments from the left ventricular free wall of canine hearts was quantified by a Clark-type O2 electrode at 37 degrees C. S-nitroso-N-acetylpenicillamine (SNAP, 9 +/- 3% to 50 +/- 8%), bradykinin (BK, 14 +/- 3% to 30 +/- 5%), or carbachol (CCh, 15 +/- 4% to 29 +/- 4%) significantly attenuated tissue O2 consumption at doses of 10(-7) to 10(-4) mol/L (mean +/- SE, P < .05). The effects of BK and CCh, but not SNAP, were blocked by 10(-4) mol/L NG-nitro-L-arginine, consistent with both BK and CCh stimulating NO biosynthesis and with SNAP decomposing to release NO, respectively. Similar doses of 8-Br-cGMP caused a respiratory inhibition, but to a lesser extent (9 +/- 2% to 14 +/- 6%). A mitochondrial uncoupler, 2,4-dinitrophenol (at 1 mmol/L), blocked the effects of 8-Br-cGMP, but not those of SNAP, BK, or CCh, suggesting that the major site of action of NO is on mitochondrial electron transport. Myocardial muscle from dogs with pacing-induced heart failure had a basal O2 consumption rate of 251 +/- 21 nmol.min-1.g-1, which was 54% higher than the rate seen in muscle from normal healthy canine hearts. The inhibitory effects of BK and CCh on O2 consumption were not observed in failing cardiac tissue, but SNAP showed an unaltered inhibitory effect. Therefore, our results indicate that NO released from microvascular endothelium by BK, stimulation of muscarinic receptors, and perhaps flow velocity may play an important physiological role in the control of cardiac mitochondrial respiration, and the loss of this regulatory function may contribute to the development of heart failure.

Conjugation of methotrexate to poly(L-lysine) increases drug transport and overcomes drug resistance in cultured cells

Methotrexate and [(3)H]methotrexate were conjugated through a carbodiimide-catalyzed reaction to a 70,000 molecular weight poly(L-lysine) in molar ratios of approximately 13 to 1. The cellular uptake of labeled conjugate was far in excess of the uptake of free drug in cells that were either proficient or deficient in methotrexate transport. The conjugate markedly inhibited the growth of PRO(-)3 Mtx(RII) 5-3 Chinese hamster ovary cells, which are known to be drug resistant by virtue of a deficient methotrexate transport. The cells, however, were not inhibited by the same concentrations of free poly(Lys) and free drug. The 100-fold difference in drug concentration needed to inhibit the mutant cells and their corresponding wild type was totally abolished by exposing the methotrexate-resistant cells to methotrexate-poly(Lys). That the drug is carried into the resistant cells as intact drug-poly(Lys) is evident also from the fact that the conjugate is rendered inactive by brief trypsinization in vitro. Because the conjugate fails to inhibit dihydrofolate reductase (5,6,7,8-tetrahydrofolate: NADP(+) oxidoreductase; EC 1.5.1.3) in vitro, it must be concluded that the strong growth inhibitory effect of the conjugate is due to the intracellular hydrolysis of its polymeric backbone, followed by the release inside the cell of a pharmacologically active form of methotrexate. Our date show that in methotrexate-resistant cells the intracellular release of active drug after uptake of conjugate is of the same order of magnitude as the uptake of free drug by transport-proficient cells and, hence, that the drug resistance due to deficient transport can be totally overcome.

Reoperation for persistent or recurrent primary hyperparathyroidism

OBJECTIVE

To analyze the causes and outcomes of reoperation for persistent or recurrent primary hyperparathyroidism.

DATA SOURCES

Medical records of 102 patients with persistent or recurrent primary hyperparathyroidism who underwent reoperation by 1 surgeon between 1985 and 1995.

STUDY SELECTION

Only patients with persistent or recurrent primary hyperparathyroidism were selected; patients with secondary hyperparathyroidism, parathyroid cancer, familial hyperparathyroidism, and previous thyroid operations were omitted.

DATA EXTRACTION

Performed by a single unblinded researcher.

DATA SYNTHESIS

Reasons for failed parathyroid operations included tumor in ectopic position (53%), incomplete resection of multiple abnormal glands (37%), adenoma in normal position missed during previous surgery (7%), and regrowth of previously resected tumor (3%). Of the ectopic glands, 28% were paraesophageal, 26% in the mediastinum (nonthymic), 24% intrathymic, 11% intrathyroidal, 9% in the carotid sheath, and 2% in a high cervical position. Eighty-three percent of ectopic glands were accessible via cervical incision. The success rate of reoperations was 95%. One patient (1%) became permanently hypocalcemic after reoperation; 1 patient (1%) suffered permanent unilateral vocal cord paralysis. The sensitivities of preoperative localization studies were as follows: technetium Tc 99m sestamibi scan, 77%; magnetic resonance imaging, 77%; selective venous catheterization for intact parathyroid hormone, 77%; thallium-technetium scan, 68%; ultrasonography, 57%; and computed tomography, 42%.

CONCLUSIONS

Repeated parathyroidectomy can be avoided in more than 95% of patients if an experienced surgeon performs bilateral cervical exploration during the initial parathyroid operation. For patients with persistent or recurrent primary hyperparathyroidism, preoperative localization studies and a focused surgical approach can result in a 95% success rate with minimum complications.

Function and production of nitric oxide in the coronary circulation of the conscious dog during exercise

This study determined the changes in NO production from the coronary circulation of the conscious dog during exercise. The role of endogenous NO as it relates to coronary flow, myocardial work, and metabolism was also studied. Mongrel dogs were chronically instrumented for measurements of coronary blood flow (CBF), ventricular and aortic pressure, and ventricular diameter, with catheters in the aorta and coronary sinus. Acute exercise (5 minutes at 3.6, 5.9, and 9.1 mph) was performed, and hemodynamic measurements and blood samples were taken at each exercise level. Nitro-L-arginine (NLA, 35 mg/kg IV) was given to block NO synthesis, and the exercise was repeated. Blood samples were analyzed for oxygen, plasma nitrate/nitrite (an index of NO), lactate, glucose, and free fatty acid (FFA) levels. Acute exercise caused significant elevations in NO production by the coronary circulation (46 +/- 23, 129 +/- 44, and 63 +/- 32 nmol/min at each speed respectively, P < .05). After NLA, there was no measurable NO production at rest or during exercise. Blockade of NO synthesis resulted in elevations in myocardial oxygen consumption and reductions in myocardial FFA consumption for comparable levels of CBF and cardiac work. The metabolic changes after NLA occurred in the absence of alterations in myocardial lactate or glucose consumptions. NO production by the coronary circulation is increased with exercise and blocked by NLA. The absence of NO in the coronary circulation during exercise does not affect levels of CBF, because it shifts the relationship between cardiac work and myocardial oxygen consumption, suggesting that endogenous NO modulates myocardial metabolism.

Conjugation of poly-L-lysine to albumin and horseradish peroxidase: a novel method of enhancing the cellular uptake of proteins

The carbodiimide-catalyzed conjugation of a 6700 molecular weight fragment of poly-L-lysine to radiolabeled human serum albumin or to horseradish peroxidase enhances the membrane transport of each protein into cultured mouse fibroblasts approximately 11- and 200-fold, respectively. At least 50% of the peroxidase activity remained after conjugation. Trypsinization and carbamylation of the two conjugates demonstrates that the enhancement of their cellular uptake is related to their poly-L-lysine content. Simple addition to the medium of comparable amounts of free poly-L-lysine has no effect on the transport of either native protein. Addition of poly-L-ornithine (molecular weight 200,000) at 3-30 microgram/ml, a condition known to cause enhancement of 125I-labeled human serum albumin uptake by mouse sarcoma cells, has no visible effect on the cellular uptake of native horseradish peroxidase. The intracellular localization of the enzyme-poly-L-lysine conjugate can be demonstrated cytochemically by either light or transmission electron microscopy. A concentration of conjugate that increases the uptake more than 200-fold does not cause any detectable morphological change suggestive of cell toxicity. Furthermore, because poly-L-lysine is an excellent substrate for intracellular proteolytic enzymes, it can be expected to be broken down and reutilized in the cell.

Involvement of polyamines in the chilling tolerance of cucumber cultivars

The possible involvement of polyamines (PAs) in the chilling tolerance of cucumber (Cucumis sativus L. cv Jinchun No. 3 and cv Suyo) was investigated. Plants with the first expanded leaves were exposed to 3 degrees C or 15 degrees C in the dark for 24 h (chilling), and then transferred to 28 degrees C/22 degrees C under a 12-h photoperiod for another 24 h (rewarming). Chilling-tolerant cv Jinchun No. 3 showed a marked increase of free spermidine (Spd) in leaves, once during chilling and again during rewarming. Putrescine increased significantly during rewarming, but the increase of spermine was slight. Any of these PAs did not increase in chilling-sensitive cv Suyo during either period. PA-biosynthetic enzyme activities appear to mediate these differences between cultivars. Pretreatment of Spd to cv Suyo prevented chill-induced increases in the contents of hydrogen peroxide in leaves and activities of NADPH oxidases and NADPH-dependent superoxide generation in microsomes and alleviated chilling injury. Pretreatment of methylglyoxal-bis-(guanylhydrazone), a PA biosynthesis inhibitor, to chilled cv Jinchun No. 3 prevented Spd increase and enhanced microsomal NADPH oxidase activity and chilling injury. The results suggest that Spd plays important roles in chilling tolerance of cucumber, probably through prevention of chill-induced activation of NADPH oxidases in microsomes.

Yeast TAF(II)145 required for transcription of G1/S cyclin genes and regulated by the cellular growth state

TFIID comprises the TATA box-binding protein and a set of highly conserved associated factors (TAF(II)s). yTAF(II)145, the core subunit of the yeast TAF(II) complex, is dispensable for transcription of most yeast genes but specifically required for progression through G1/S. Here we show that transcription of G1 and certain B-type cyclin genes is dependent upon yTAF(II)145. At high cell density or following nutrient deprivation, yeast cells cease division, enter a G0-like state, and terminate transcription of most genes. In this stationary phase, we find that the levels of yTAF(II)145, several other yTAF(II)s, and TBP are drastically reduced. Collectively, our results indicate that yTAF(II)145 and other TFIID components have a specialized role in transcriptional regulation of cell cycle progression and growth control.

Hepatocyte nuclear factor 3beta (Foxa2) is dispensable for maintaining the differentiated state of the adult hepatocyte

Liver-specific gene expression is controlled by a heterogeneous group of hepatocyte-enriched transcription factors. One of these, the winged helix transcription factor hepatocyte nuclear factor 3beta (HNF3beta or Foxa2) is essential for multiple stages of embryonic development. Recently, HNF3beta has been shown to be an important regulator of other hepatocyte-enriched transcription factors as well as the expression of liver-specific structural genes. We have addressed the role of HNF3beta in maintenance of the hepatocyte phenotype by inactivation of HNF3beta in the liver. Remarkably, adult mice lacking HNF3beta expression specifically in hepatocytes are viable, with histologically normal livers and normal liver function. Moreover, analysis of >8,000 mRNAs by array hybridization revealed that lack of HNF3beta affects the expression of only very few genes. Based on earlier work it appears that HNF3beta plays a critical role in early liver development; however, our studies demonstrate that HNF3beta is not required for maintenance of the adult hepatocyte or for normal liver function. This is the first example of such functional dichotomy for a tissue specification transcription factor.