Gender difference in the cycle length-dependent QT and potassium currents in rabbits

Women are known to have a longer electrocardiographic Q-T than men, which may contribute to their being at greater risk of developing drug-induced polymorphic ventricular arrhythmias. However, little is known about the underlying mechanisms. In the present study, we evaluated potential gender differences in Q-T interval in isolated perfused rabbit hearts using the Langendorff technique and evaluated the density of outward potassium currents in single ventricular myocytes using the whole-cell patch-clamp technique. We found that female hearts demonstrated a greater Q-T lengthening (delta Q-T%) upon an increase in cycle length (CL), resulting in a significantly longer Q-T (301 +/- 4.8 ms, CL = 2.3 s) at a long CL in female hearts compared with male hearts (267 +/- 4.0 ms, P < .01). Ventricular myocytes isolated from female hearts showed a smaller IK(tail) and peak IKI outward current density. A 50% reduction in extracellular K+ and Mg++ shifted the I-V relationship of IKI and Ito and reduced their amplitude. However, neither the I-V relationship of IKr nor the gender difference in the Q-T-CL relationship was significantly altered. We conclude that 1) female rabbit ventricular myocytes have significantly lower IKr and IKl outward current densities than do male cells, which may contribute to the gender difference in Q-T, and 2) a lower base-line IKr density may contribute to the steeper Q-T-CL relationship in female hearts.     

Evaluation of a novel hirudin-coated polyester graft to physiologic flow conditions: hirudin bioavailability and thrombin uptake

PURPOSE: Our laboratory has developed methods required to covalently bind recombinant hirudin (rHir) to the surface of polyester vascular grafts. Using alkaline hydrolysis of the polyester surface, carboxyl-binding sites are created on the outer periphery of each fiber. A series of static, in vitro experiments have demonstrated that surface-bound rHir rapidly removes and inhibits activated human alpha-thrombin from the reaction system; however, the performance of this modified graft material under physiologic flow conditions was undefined. METHODS: An in vitro flow loop was used to evaluate structural stability of the 125I-rHir and 131I-albumin covalently bound to the surface of 6 mm interior diameter crimped polyester grafts exposed to either constant flow (n = 4; shear rate, 300 sec(-1)) or pulsatile flow (n = 4; maximum shear rate, 780 sec(-1)) conditions for a 7-day period. In a separate series of experiments, the kinetics of thrombin-rHir interaction were evaluated through perfusion of 125I-rHir-coated grafts (n = 6) with 131I-thrombin for a 27-hour period under constant flow conditions. Identically prepared 125I-albumin-coated grafts (n = 3) were used as controls. RESULTS: Results of the stability experiments were independent of flow conditions, demonstrating moderate loss of both proteins, with rHir and albumin losses of 52.1% and 19.9% under constant flow and 49.1% and 21.6% under pulsatile flow, respectively. With results comparable with those of previous static experiments, rHir-coated grafts were significantly more effective at removing thrombin from the perfusion stream with 131I-thrombin binding densities of 3.08 +/- 0.61 and 0.64 +/- 0.04 NIHU/cm2 (p < 0.01) for rHir-coated and albumin-coated grafts, respectively. Estimates of the total amount of thrombin inactivated during the perfusion period similarly demonstrated a marked difference between the rHir-coated and control graft segments (125 +/- 8 vs. 3 +/- 14 NIHU; p < 0.005). CONCLUSIONS: These in vitro flow results illustrate that polyester grafts with covalently bound rHir can provide significant reductions in local thrombin concentration under physiologic flow conditions, and can serve as a foundation with which to understand the performance of these grafts when implanted in vivo under physiologic flow and shear rates.     

High-resolution microscopic determination of hepatic NADH fluorescence for in vivo monitoring of tissue oxygenation during hemorrhagic shock and resuscitation

Psychopharmacological studies using caffeinated beverages or caffeine have rarely considered temporal effects on psychological and physiological function or the specific contribution of caffeine, hot water, or beverage type to the observed effects. The effect of 400 ml hot tea, coffee, and water consumption on systolic and diastolic blood pressure (SBP and DBP), heart rate, skin conductance (a measure of sympathetic nervous system activation), skin temperature, salivary cortisol, and mood were monitored in 16 healthy caffeine-withdrawn (14 h) subjects in a complete crossover design. Beverages were ingested with/without 100 mg caffeine and milk (tea/coffee only). Hot beverage ingestion rapidly increased skin conductance and temperature (+1.7 degrees C) with peak effects observed only 10-30 min post-consumption. Caffeine in the beverage rapidly augmented skin conductance responses but, in contrast to the effect of hot water, reduced the skin temperature response and increased SBP (+2.8 mmHg) and DBP (+2.1 mmHg) 30-60 min post-consumption. Both caffeine and milk addition to beverages independently improved mood and reduced anxiety 30 and 60 min post-consumption. Milk addition had no other effects apart from attenuating the transient increase in physiological responses associated with the drinking phase. There were no effects of beverage consumption on salivary cortisol or of beverage vehicle on salivary caffeine levels, the latter indicating that caffeine pharmacokinetics was similar in both tea and coffee, and not different from caffeinated water. In keeping with this, the responses to tea and coffee ingestion were similar and largely accounted for by the effects of hot water and caffeine. However, tea potentiated the increase in skin temperature compared to coffee and water indicative of a greater vasodilatory response plausibly related to the presence of flavonoids in tea. We conclude that ingestion of hot caffeinated beverages stimulates physiological processes faster than hitherto described, primarily via the effects of hot water and caffeine, but with beverage type and milk playing important modulatory roles.     

Lactose maldigestion is not an impediment to the intake of 1500 mg calcium daily as dairy products

BACKGROUND: A National Institutes of Health consensus conference concluded that a daily calcium intake of 1500 mg reduces the severity of osteoporosis. Because dairy products are the main natural source of dietary calcium, a diet providing 1500 mg Ca must contain large quantities of dairy products. However, it is widely believed that the lactose content of these products will not be tolerated by persons with lactose maldigestion (approximately 30% of the adult US population). OBJECTIVE: We evaluated the symptoms of lactose maldigestion and digestion when the diet was supplemented with dairy products providing 1300 mg Ca/d. DESIGN: Sixty-two women (31 with lactose maldigestion and 31 without) were studied in a double-blind, randomized protocol. Symptoms were compared during 1-wk periods when the diet was supplemented with 480 mL (2 cups) milk, 56 g cheese, and 240 mL yogurt provided as conventional products (34 g lactose/d) or as lactose-hydrolyzed products (2 g lactose/d). RESULTS: Women who digested lactose reported no significant difference in symptoms between the 2 treatment periods. Women with lactose maldigestion reported significantly increased flatus frequency and subjective impression of rectal gas during the period of high lactose intake; however, bloating, abdominal pain, diarrhea, and the global perception of overall symptom severity were not significantly different between the 2 treatment periods. CONCLUSION: The symptoms resulting from lactose maldigestion are not a major impediment to the ingestion of a dairy-rich diet supplying approximately 1500 mg Ca/d.     

Changes with aging, sex and physical exercise in murine natural killer activity and antibody-dependent cellular cytotoxicity

Antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activity were measured in leukocytes from the axillary nodes, the spleen and the thymus of young (12 +/- 2 weeks) and aged (60 +/- 2 weeks) male and female BALB/c mice, which had performed an acute bout of exercise (moderate swimming until exhaustion) or a training exercise (90 min of moderate swimming each day for 20 days). The results show that NK and ADCC activity in sedentary mice (controls) were similar in young and aged animals. However, both kinds of exercise resulted in higher cytotoxicity values in aged mice than in young mice. Acute exercise did not have any effect on NK activity in young and aged mice, nor on ADCC activity in young mice as compared to controls, while training exercise stimulated both cytotoxicities in the two age groups. No correlations between serum corticosterone levels and NK or ADCC activity were found. Our results suggest that moderate training exercise improves both NK and ADCC activity during aging.     

Homozygous deletions of methylthioadenosine phosphorylase (MTAP) are more frequent than p16INK4A (CDKN2) homozygous deletions in primary non-small cell lung cancers (NSCLC)

Homozygous deletions of the tumor suppressor gene p16INK4A and deficiency of methylthioadenosine phosphorylase (MTAP), both located on chromosome 9p21, have been independently reported in non-small cell lung cancer (NSCLC). To determine the frequency of co-deletion of these two genes, we investigated 50 samples of primary NSCLC using a quantitative PCR-ELISA. All specimens were fixed in formalin, paraffin embedded and stored until assayed. Histologic subtypes included 25 adenocarcinomas (50%), 21 squamous cell carcinomas (42%) and four large cell carcinomas (8%). Homozygous deletions of MTAP exon 8 could be detected in 19 of 50 NSCLC samples (38%). Adenocarcinoma (11 of 25, 44%) showed a higher deletion frequency than squamous cell carcinoma (six of 21, 29%). In contrast, homozygous p16INK4A deletions were detected in only nine of 50 (18%) samples using specific primers for p16INK4A exon 1alpha. No difference between the histological subtypes and p16INK4A deletion frequency was observed. We further investigated the ten samples with MTAP deletions but intact p16INK4A exon 1alpha with primers specific for p16INK4A exon 3, the exon nearest to MTAP exon 8. Interestingly, none of the ten samples had deletion of the p16INK4A exon 3 coding region. Fine mapping analysis performed in ten samples showed a frequent breakpoint between MTAP exon 4 and exon 5. In addition, p16 protein expression could not be detected in five out of six samples with intact p16 but deleted MTAP locus. These data show a high frequency of homozygous MTAP deletions in NSCLC which is associated with detectable co-deletion of p16INK4A in only half of the cases. This result suggests the existence either of another tumor suppressor gene telomeric of p16INK4A or of deletions involving 3'-untranslated (3'-UTR) regulatory regions of p16INK4A that can interfere with its expression or function.     

Very distal bypass for salvage of the severely ischemic extremity

Forty-six bypass grafts to tibial arteries distal to the ankle were performed in 35 patients for salvage of extremities threatened by gangrene or nonhealing ulcers (grade III, category 5) or ischemic rest pain (grade II, category 4). Most patients (80%) were diabetic, with severely calcified arteries, whom previously we would have considered as candidates for primary amputation. All reconstructions were performed with autologous saphenous vein. Inflow was from the common femoral artery in 5 (11%), the popliteal artery in 25 (54%), or the mid-tibial arteries in 16 (35%). Life-table analysis was used to calculate primary patency and limb salvage. Results were analyzed according to origin of inflow, outflow, or configuration of the conduit (in situ saphenous vein, n = 29 [63%], reversed saphenous vein, n = 11 [24%], or nonreversed saphenous vein, n = 6 [13%]). Overall cumulative primary graft patency at 2 years for all grafts was 72%, and the cumulative limb salvage rate was 89% for the same interval. No significant differences were seen in comparing grafts originating from the femoral or popliteal level with those arising from the tibial arteries. No significant differences were noted in graft patency or limb salvage among grafts with a posterior tibial, dorsalis pedis, or plantar artery outflow. No significant difference was noted between in situ saphenous vein grafts and reversed saphenous vein grafts. A significant decreased primary patency was noted for grafts performed with nonreversed, translocated saphenous vein. We conclude that bypass grafts to the ankle or foot vessels are beneficial and should be considered for limb salvage in extremities with gangrene, ischemic ulceration, or ischemic rest pain. In our experience, in situ saphenous vein grafts or reversed saphenous vein grafts performed similarly, whereas nonreversed saphenous vein grafts have a poorer prognosis. Vessel wall calcification requires a modification in technique for performance of these grafts but did not affect long-term performance or limb salvage, and thus should not be considered a contraindication to vascular reconstruction. The operative microscope was used in 61% (28 of 46) of these cases and found useful in creating these delicate anastomoses. Additional follow-up is needed to document the long-term results of these very distal reconstructions.     

Bacterial lipopolysaccharide induces uncoupling protein-2 expression in hepatocytes by a tumor necrosis factor-alpha-dependent mechanism

The liver is a target for bacterial lipopolysaccharide (LPS) and participates in the metabolic response to endotoxemia. Recently published evidence indicates that LPS increases the expression of mitochondrial uncoupling protein-2 (UCP-2) mRNAs in several tissues, including the liver. Because hepatocytes in the healthy liver do not express UCP-2, LPS was thought to induce UCP-2 in liver macrophages, which express UCP-2 constitutively. However, the present studies of cultured peritoneal macrophages indicate that LPS reduces steady state levels of UCP-2 mRNAs in these cells. In contrast, UCP-2 mRNAs are induced in hepatocytes isolated from LPS treated rats and transfection of these hepatocytes with UCP-2 promoter-reporter constructs demonstrates substantial increases in UCP-2 promoter activity. LPS induction of hepatocyte UCP-2 expression is virtually abolished by prior treatment of rats with neutralizing antibodies to tumor necrosis factor alpha (TNF). Futhermore, TNFalpha treatment induces UCP-2 mRNA accumulation in primary cultures of hepatocytes from healthy rats. Thus, hepatocytes are likely to be important contributors to endotoxin-related increases in liver UCP-2 via a mechanism that involves the LPS-inducible cytokine, TNFalpha.