Glassy cell carcinoma of the uterine cervix

15050

Background: Glassy Cell Carcinoma of the uterine cervix is a rare, aggressive form of cervical cancer accounting for only 1–5% of all cervical carcinomas. To date, there is no consensus on treatment modalities, but most advocate for a more aggressive treatment strategy including both radical surgery and radiation therapy. The objective of this study was to analyze the clinical features, treatment, and outcome of patients with Glassy cell carcinoma diagnosed at our institution. We hypothesized that such aggressive therapies yield survival benefits which approximate those of the more common squamous cell carcinomas of the cervix. Methods: In collaboration with the Department of Radiation Oncology at Rhode Island Hospital, a retrospective comprehensive chart review of all patients diagnosed with Glassy cell carcinoma of the cervix between the years 1993 and 2005 was undertaken at Women and Infant’s Hospital, Providence, RI. All cases were assessed for clinicopathologic features, treatment strategies, and outcome, including progression free survival and overall survival rates. Results: Twenty-eight patients with biopsy proven Glassy Cell Carcinoma of the cervix were identified. Eleven (39%) were less than age 40, and five (18%) were less than age 30. Of these, 19 were either stage IB or IIA, and 15/19 (79%) received multimodality therapy, a combination of radiation, chemotherapy, and surgery, as initial treatment. When survival was broken down by mode of treatment, 25% of patients who received single modality treatment (either surgery or radiation) were DF at two and five years. In contrast, those patients who were treated with bimodal therapy had a DFS of 93% at 2 years and 84% at 5 years. Thus the survival of patients with glassy cell histology treated at our institution with multimodality therapy approximates the survival of similar stage patients with squamous and adenocarcinoma, with a mean follow-up of greater than 5 years. This represents a distinct improvement when compared to national survival statistics. Conclusions: The favorable survival results of this aggressively treated population, supports the belief that multimodality therapy is preferable in patients with glassy cell carcinoma of the cervix even in early stage disease. However, optimal treatment regimens have yet to be determined and is a field for further study.

No significant financial relationships to disclose.

Acute and chronic effects of relaxin on vasoactivity, myogenic reactivity and compliance of the rat mesenteric arterial and venous vasculature

We investigated the effect of relaxin on vasodilation, myogenic reactivity, and compliance of small mesenteric arteries and veins. In acute experiments, small (second order) mesenteric arteries and veins from female rats were mounted in a pressure myograph, perfused intraluminally with relaxin, and exposed to incremental increases in intraluminal pressure (20-120 mm Hg for arteries, 2-12 mm Hg for veins). We expressed myogenic reactivity as the ratio of active to passive diameter at each pressure step. In chronic experiments, relaxin was administered to rats (4 microg/h) for 3 days prior to isolating the vessels and measuring myogenic reactivity. Arteries were more sensitive than were veins to the acute vasodilatory activity of relaxin (EC50: arteries=1.32+/-0.18x10(-8) M; veins=3.19+/-0.88x10(-8) M, P<0.05). Acute relaxin reduced myogenic reactivity of mesenteric arteries, but not veins. Chronic pretreatment with relaxin did alter the pressure/diameter relationship in Ca(2+)-containing medium, but this was due to increased passive compliance (control: 2.96+/-0.14 microm mm Hg(-1), n=5; relaxin: 3.72+/-0.16 microm mm Hg(-1), n=5) rather than to reduced myogenic reactivity. Chronic relaxin did not alter myogenic reactivity or compliance (control: 43.8+/-1.4 microm mm Hg(-1), n=5; relaxin: 46.1+/-2.3 microm mm Hg(-1), n=5) of veins. Thus, although relaxin reduces total peripheral resistance, it does not affect splanchnic venous capacitance or tone. In the face of elevated plasma relaxin levels, such as during pregnancy, cardiac preload may thus be maintained, concurrent with a reduction in cardiac afterload and blood pressure. We caution that, if an experimental treatment alters compliance, myogenic reactivity must be expressed as the ratio of active:passive diameter.

Splenic baroreceptors control splenic afferent nerve activity

Stenosis of either the portal or splenic vein increases splenic afferent nerve activity (SANA), which, through the splenorenal reflex, reduces renal blood flow. Because these maneuvers not only raise splenic venous pressure but also reduce splenic venous outflow, the question remained as to whether it is increased intrasplenic postcapillary pressure and/or reduced intrasplenic blood flow, which stimulates SANA. In anesthetized rats, we measured the changes in SANA in response to partial occlusion of either the splenic artery or vein. Splenic venous and arterial pressures and flows were simultaneously monitored. Splenic vein occlusion increased splenic venous pressure (9.5 +/- 0.5 to 22.9 +/- 0.8 mmHg, n = 6), reduced splenic arterial blood flow (1.7 +/- 0.1 to 0.9 +/- 0.1 ml/min, n = 6) and splenic venous blood flow (1.3 +/- 0.1 to 0.6 +/- 0.1 ml/min, n = 6), and increased SANA (1.7 +/- 0.4 to 2.2 +/- 0.5 spikes/s, n = 6). During splenic artery occlusion, we matched the reduction in either splenic arterial blood flow (1.7 +/- 0.1 to 0.7 +/- 0.05, n = 6) or splenic venous blood flow (1.2 +/- 0.1 to 0.5 +/- 0.04, n = 5) with that seen during splenic vein occlusion. In neither case was there any change in either splenic venous pressure (-0.4 +/- 0.9 mmHg, n = 6 and +0.1 +/- 0.3 mmHg, n = 5) or SANA (-0.11 +/- 0.15 spikes/s, n = 6 and -0.05 +/- 0.08 spikes/s, n = 5), respectively. Furthermore, there was a linear relationship between SANA and splenic venous pressure (r = 0.619, P = 0.008, n = 17). There was no such relationship with splenic venous (r = 0.371, P = 0.236, n = 12) or arterial (r = 0.275, P = 0.413, n = 11) blood flow. We conclude that it is splenic venous pressure, not flow, which stimulates splenic afferent nerve activity and activates the splenorenal reflex in portal and splenic venous hypertension.

Left coronary artery arising from the non-coronary sinus: a rare congenital coronary anomaly

Anomalous origin of the left coronary artery is a cause of sudden death in adolescents and young adults. Most commonly, it originates from the right coronary sinus or the pulmonary artery. Origin of the left main coronary artery from the non-coronary sinus of Valsalva is extremely rare. We report a case of a child with anomalous origin of the left main coronary artery from the non-coronary sinus diagnosed during the evaluation of a ventricular arrhythmia.

Repeated pregnancies (multiparity) increases venous tone and reduces compliance

In humans, multiparity (repeated pregnancy) is associated with increased risk of cardiovascular disease. In rats, multiparity increases the pressor response to phenylephrine and to acute stress, due in part to changes in tone of the splanchnic arterial vasculature. Given that the venous system also changes during pregnancy, we studied the effects of multiparity on venous tone and compliance. Cardiovascular responses to volume loading (2 ml/100 g body wt), and mean circulatory filling pressure (MCFP, an index of venomotor tone) were measured in conscious, repeatedly bred (RB), and age-matched virgin rats. In addition, passive compliance and venous reactivity of isolated mesenteric veins were measured by pressure myography. There was a greater increase in mean arterial pressure after volume loading in RB rats (+7.2 ± 2.5 mmHg, n = 8) than virgin rats (−1.4 ± 1.7 mmHg, n = 7) ( P < 0.05). The increase in MCFP in response to norepinephrine (NE) was also greater in RB rats [half maximal effective dose (ED50) 3.1 ± 0.5 nmol·kg−1·min−1, n = 6] than virgins (ED50: 12.1 ± 2.7 nmol·kg−1·min−1, n = 6) ( P < 0.05). Pressure-induced changes in passive diameter were lower in isolated mesenteric veins from RB rats (29.3 ± 1.8 μm/mmHg, n = 6) than from virgins (36.9 ± 1.3 μm/mmHg, n = 6) ( P < 0.05). Venous reactivity to NE in isolated veins was also greater in RB rats (EC50: 2.68 ± 0.37×10−8 M, n = 5) than virgins (EC50: 4.67 ± 0.93 × 10−8 M, n = 8). We conclude that repeated pregnancy induces a long-term reduction in splanchnic venous compliance and augments splanchnic venous reactivity and sympathetic tonic control of total body venous tone. This compromises the ability of the capacitance (venous) system to accommodate volume overloads and to buffer changes in cardiac preload.

Effects of atrial natriuretic peptide on the extrasplenic microvasculature and lymphatics in the rat in vivo

We developed a novel model using fluorescent intravital microscopy to study the effect of atrial natriuretic peptide (ANP) on the extrasplenic microcirculation. Continuous infusion of ANP into the splenic artery (10 ng min(-1) for 60 min) of male Long-Evans rats (220-250 g, n = 24) induced constriction of the splenic arterioles after 15 min (-7.2 +/- 6.6% from baseline diameter of 96 +/- 18.3 microm, mean +/- S.E.M.) and venules (-14.4 +/- 4.0% from 249 +/- 25.8 microm; P < 0.05). At the same time flow did not change in the arterioles (from 1.58 +/- 0.34 to 1.27 +/- 0.27 ml min(-1)), although it decreased in venules (from 1.67 +/- 0.23 to 1.15 +/- 0.20 ml min(-1)) and increased in the lymphatics (from 0.007 +/- 0.001 to 0.034 +/- 0.008 ml min(-1); P < 0.05). There was no significant change in mean arterial pressure (from 118 +/- 5 to 112 +/- 5 mmHg). After continuous ANP infusion for 60 min, the arterioles were dilated (108 +/- 16 microm, P < 0.05) but the venules remained constricted (223 +/- 24 microm). Blood flow decreased in both arterioles (0.76 +/- 0.12 ml min(-1)) and venules (1.03 +/- 0.18 ml min(-1); P < 0.05), but was now unchanged from baseline in the lymphatics (0.01 +/- 0.001 ml min(-1)). This was accompanied by a significant decrease in MAP (104 +/- 5 mmHg; P < 0.05). At 60 min, there was macromolecular leak from the lymphatics, as indicated by increased interstitial fluorescein isothiocyanate-bovine serum albumin fluorescence (grey level: 0 = black; 255 = white; from 55.8 +/- 7.6 to 71.8 +/- 5.9, P < 0.05). This study confirms our previous proposition that, in the extrasplenic microcirculation, ANP causes greater increases in post- than precapillary resistance, thus increasing intrasplenic capillary hydrostatic pressure (P(c)) and fluid efflux into the lymphatic system. Longer-term infusion of ANP also increases Pc, but this is accompanied by increased 'permeability' of the extrasplenic lymphatics, such that fluid is lost to perivascular third spaces.

Effect of pregnancy and 5α-pregnan-3α-ol-20-one on atrial receptor afferent discharge in rats

The atrial volume reflex is attenuated in pregnancy. This may be mimicked by chronic administration of 5α-pregnan-3α-ol-20-one (pregnan). We investigated whether afferent output from sensory receptors may be suppressed at this time. Vagal afferent nerve activity was measured during discrete localized stimulation of the atrial volume receptors by inflation of a balloon at the superior vena caval-right atrial junction. The receptors were classified as high- (HF) or low- (LF) frequency subtypes on the basis of their response to graded atrial distension. Although both HF (regression coefficient = 0.50 ± 0.11 Hz/μl, r2 = 0.47, P < 0.001) and LF (regression coefficient = 0.03 ± 0.05 Hz/μl, r2 = 0.009, P = 0.613) subtypes could be identified in virgin rats, only LF (regression coefficient = 0.09 ± 0.05 Hz/μl, r2 = 0.044, P = 0.099) receptors were found in late-pregnant animals. Similarly, in virgin rats treated chronically with pregnan (500 μg/24 h for 2 days), only LF receptors were identified (regression coefficient = −0.004 ± 0.078 Hz/μl, r2 = 0.000, P = 0.962), whereas both subtypes were present in the vehicle-treated animals (HF regression coefficient = 0.626 ± 0.255 Hz/μl, r2 = 0.317, P = 0.029; LF regression coefficient = −0.012 ± 0.071 Hz/μl, r2 = 0.002, P = 0.866). By contrast, acute intracardiac pregnan (2.6 μg/kg) did not alter vagal afferent nerve activity. In conclusion, stretch-induced discharge of high-frequency atrial receptors is suppressed during pregnancy, whereas that of low-frequency receptors is preserved. This effect may be mimicked by chronic, but not acute, pregnan. We propose that, during pregnancy, pregnan alters the transducer properties of the atrial volume receptors, thus allowing blood volume to increase.

Long-term effects of repeated pregnancies (multiparity) on blood pressure regulation

OBJECTIVE

Pregnancy is associated with profound alterations in the cardiovascular system, the long-term effects of which are unknown. Human epidemiological studies suggest that multiparity (multiple pregnancies) increases the risk of cardiovascular disease. The mechanisms underlying these findings remain to be elucidated. The objective of this study was to determine the long-term effects of parity on cardiovascular regulation.

METHODS

Pressor responses to phenylephrine (PE) and acute stress were compared in conscious age-matched repeatedly breed (RB) and virgin rats. Vascular compliance and reactivity of isolated resistance-sized mesenteric arteries were studies using pressure and wire myograph.

RESULTS

We found that both exogenous PE and acute stress elicited greater pressor responses in RB than in aged-matched virgins. Pressure and wire myography also revealed that small mesenteric arteries from RB rats were less compliant than those from virgins (RB: 0.24+/-0.04 microm mm Hg(-1), n=6 vs. virgins: 0.63+/-0.06 microm mm Hg(-1), n=6; p< or =0.05) and were more sensitive to PE (EC(50) RB: 1.58+/-0.08 x 10(-6) M, n=10 vs. virgins: 2.05+/-0.09 x 10(-6) M, n=14; p< or =0.05). Removal of the endothelium abolished the difference in sensitivity. More specifically, the augmented vascular response of RB was both nitric oxide (NO) and cyclooxygenase dependent. By contrast, there was no difference in methacholine-induced vasodilation of phenylephrine-preconstricted vessels.

CONCLUSION

Our results suggest that repeated pregnancies induce long-term alterations in cardiovascular regulation due to changes in vascular compliance and endothelium-dependent vasoconstriction. We propose that such changes might influence the risk for cardiovascular disease in multiparous women.

Splenorenal reflex modulates renal blood flow in the rat

We have previously shown that the splenorenal reflex controls renin release through splenic afferent and renal sympathetic nerves. We proposed that this reflex would also affect renal blood flow (RBF). RBF was measured in male Long Evans rats using transit-time flow probes. There were no significant differences between any of the experimental groups with respect to baseline values of RBF (8.9 +/- 0.4 ml min(-1), n= 25) or mean arterial pressure (MAP, 98.7 +/- 2.5 mmHg, n= 25). Splenic venous pressure was selectively raised (from 7.9 +/- 0.6 to 21.6 +/- 0.3 mmHg, n= 25) in anaesthetized rats by partial ligation of the splenic vein. This caused an immediate fall in RBF (-2.1 +/- 0.2 ml min(-1), n= 7) and in MAP (-12.4 +/- 2.8 mmHg, n= 7). The fall in RBF, but not the fall in blood pressure, was attenuated by renal denervation (DeltaRBF: - 0.7 +/- 0.1 ml min(-1), n= 6), splenic denervation (DeltaRBF: -0.8 +/- 0.1 ml min(-1), n= 6) and close renal arterial injection of the alpha1-adrenergic blocker phenoxybenzamine (12.5 microg; DeltaRBF: -0.8 +/- 0.1 ml min(-1), n= 6). Renal conductance fell only in the intact control group, i.e. the residual fall in RBF in the denervated and phenoxybenzamine-treated animals could be attributed to the fall in MAP. We also showed that splenic vein occlusion increased both splenic afferent (from 3.0 +/- 0.3 to 6.6 +/- 0.6 spikes s(-1), n= 5) and renal efferent (from 24.8 +/- 2.0 to 50.2 +/- 4.9 spikes s(-1), n= 9) nerve activity. We conclude that obstruction to splenic venous outflow, such as would occur in portal hypertension, initiates increased splenic afferent nerve activity and renal vasoconstriction through the splenorenal reflex, as well as a fall in blood pressure. We propose that this contributes to the renal and cardiovascular dysfunction observed in portal hypertension.

A vibrator prevents streaming during close-arterial infusion into the kidney

Close-arterial infusion of test substances allows one to study the responses of a selected vascular bed without inducing confounding systemic effects. Unfortunately, laminar flow patterns within the artery cause streaming of the injected factor, so that distribution within the target organ is not homogeneous. We describe a reliable method of overcoming these problems. Specifically, we attach a vibrator (i-Vibe egg) to the syringe containing the test substance. We showed that, without vibration, infusion of a solution of Evans blue (0.5% wt/vol) results in uneven distribution of the dye in the kidney. Vibration of the syringe during infusion allows for uniform coloration of the kidney surface. There is also functional improvement of drug distribution during vibration. Renal blood flow was measured during intrarenal infusion of phenylephrine (150 μl, 0.05–0.5 μg). Vibration caused a significant leftward shift in the dose-response curve, i.e., the phenylephrine-induced reduction in renal blood flow was enhanced by vibration. This cheap, simple method for ensuring adequate mixing of intra-arterially infused substances will facilitate not only the study of renal function in the rat but also infusion of test and therapeutic substances into other organs.

Capsaicin-sensitive neural pathway mediates atrial natriuretic factor (ANF) release in response to physiological stimuli

Increases in intravascular volume are detected by mechanoreceptors situated at the junctions of the great veins with the atria. We had previously shown that localized distension of the superior vena caval/right atrial junction, simulating increased cardiac preload, elicits release of ANF remotely from the atrial appendage. We proposed that ANF secretion is stimulated via intrinsic neural pathways running from the venoatrial junctions to the appendage. We developed a technique whereby non-adrenergic, non-cholinergic sensory nerves could be selectively destroyed in the heart of adult rats by instilling capsaicin into the pericardial space. Four days later, the animals were killed, and isolated perfused atria were prepared with small balloons positioned so that the superior vena caval/right atrial junction could be discretely stretched. Immunoreactive ANF secretion into the perfusate was measured. Although distension of the venoatrial junction increased ANF secretion from the control atria, there was no such response in the denervated atria. We conclude (A) that local application of capsaicin to the heart of adult rats induces selective functional neural deficits and (B) that information regarding distension of the junction of the great veins and the atria is normally transmitted across the atrium via these nerves to stimulate ANF secretion from peptide stores located in the atrial appendage. We propose that these pathways are crucial to ensure appropriate ANF secretion in response to an increase in circulating blood volume.

Neurokinin B causes concentration-dependent relaxation of isolated human placental resistance vessels

Placental neurokinin B (NKB) was recently identified as the causative agent in preeclampsia, a condition characterized by increased maternal and feto-placental vascular resistance. We hypothesized that NKB should constrict placental resistance vessels. Placentas were obtained from normotensive pregnancies. Immediately after delivery, stem villous arteries (300 microm diameter, 1.2 mm long) were dissected from macroscopically normal tissue in cold HEPES-physiological salt solution (PSS), mounted on a wire myograph system, and bathed in HEPES-PSS at 37 degrees C. After determination of the passive-tension internal circumference characteristics, the arteries were set to 90% of the internal circumference they would have under a normal physiological transmural pressure. Cumulative concentration-response curves were constructed for NKB (1 x 10(-12) to 1 x 10(-5) mol/l). Since there was no constrictive response to NKB, cumulative constrictive concentration-response curves were constructed to the thromboxane A(2) mimetic U46619 (1 x 10(-9) to 1 x 10(-5) mol/l). The vessels were then pre-constricted to 80% of maximal response and exposed to cumulative concentrations of NKB (1 x 10(-12) to 1 x 10(-6) mol/l). NKB caused a concentration-dependent relaxation (Maximal response NKB, 51+/-5%, n=5; time control, 12+/-6%, n=4; P<0.05). Removal of the endothelium did not alter the vasodilatory response to NKB. We conclude that, contrary to our hypothesis, NKB causes an endothelium-independent relaxation of the placental resistance vessels. We propose that NKB plays a role in the maintenance of high placental blood flow in normal pregnancy.

Adrenomedullin Is Decreased in Preeclampsia Because of Failed Response to Epidermal Growth Factor and Impaired Syncytialization

To explore the mechanisms of adrenomedullin (ADM) regulation in normal and preeclamptic (PE) states, we determined placental production of ADM and ADM regulation by cytokines. Isolated, purified cytotrophoblast cultures from normal (n=8) and PE (n=10) placentas were cultured for 3 days in the absence or presence of 10 ng/mL epidermal growth factor (EGF), 1 ng/mL transforming growth factor (TGF)-β1, 10 ng/mL tumor necrosis factor (TNF)-α, or 100 U/mL interferon (IFN)-γ. Cells were also cultured for 3 days in 10% fetal bovine serum for determination of syncytial formation by desmoplakin staining. Pieces of normal and PE placentas were snap-frozen for ADM mRNA measurement. Results showed that basal ADM production into culture medium by radioimmunoassay was significantly lower in PE placental cells. EGF significantly stimulated ADM production in normal trophoblasts but did not in PE placentas. None of the factors TNF-α, TGF-β1, or IFN-γ altered ADM secretion in either normal or PE placentas. ADM expression by Northern blot analysis demonstrated a 34.3±8.3% reduction in mRNA expression in PE placentas. Syncytialization, as assessed by desmoplakin-outlined syncytial units, was decreased in PE placentas (day 3: normal, 16.7±1.3%; PE, 5.5±2.0%; P <0.01, ANOVA). However, there was a normal increment in syncytialization in response to EGF in normal and PE trophoblast preparations (EGF day 3: normal, 43.8±5.6%; PE, 46.1±12.3%). We conclude that spontaneous placental syncytialization is impaired in PE and that ADM production is markedly reduced in PE, possibly owing to an impaired EGF response. These abnormalities indicate poor placental production of ADM as the likely cause of a failed compensatory increase in maternal serum ADM levels in PE.

Effect of portal hypertension on splenic blood flow, intrasplenic extravasation and systemic blood pressure

We have previously shown that intrasplenic fluid extravasation is important in controlling blood volume. We proposed that, because the splenic vein flows in the portal vein, portal hypertension would increase splenic venous pressure and thus increase intrasplenic microvascular pressure and fluid extravasation. Given that the rat spleen has no capacity to store/release blood, intrasplenic fluid extravasation can be estimated by measuring the difference between splenic arterial inflow and venous outflow. In anesthetized rats, partial ligation of the portal vein rostral to the junction with the splenic vein caused portal venous pressure to rise from 4.5 +/- 0.5 to 12.0 +/- 0.9 mmHg (n = 6); there was no change in portal venous pressure downstream of the ligation, although blood flow in the liver fell. Splenic arterial flow did not change, but the arteriovenous flow differential increased from 0.8 +/- 0.3 to 1.2 +/- 0.1 ml/min (n = 6), and splenic venous hematocrit rose. Mean arterial pressure fell (101 +/- 5.5 to 95 +/- 4 mmHg). Splenic afferent nerve activity increased (5.6 +/- 0.9 to 16.2 +/- 0.7 spikes/s, n = 5). Contrary to our hypothesis, partial ligation of the portal vein caudal to the junction with the splenic vein (same increase in portal venous pressure but no increase in splenic venous pressure) also caused the splenic arteriovenous flow differential to increase (0.6 +/- 0.1 to 1.0 +/- 0.2 ml/min; n = 8). The increase in intrasplenic fluid efflux and the fall in mean arterial pressure after rostral portal vein ligation were abolished by splenic denervation. We propose there to be an intestinal/hepatic/splenic reflex pathway, through which is mediated the changes in intrasplenic extravasation and systemic blood pressure observed during portal hypertension.

Guanylyl cyclase mediates ANP-induced vasoconstriction of murine splenic vessels

We have previously shown that ANP causes differential constriction of the splenic vasculature of the rat (veins greater than arteries), which may be inhibited by blocking the production of cGMP with A7195. In this paper, we report experiments done on vessels derived from guanylyl cyclase (GC)-A knockout mice. Small splenic arteries ( approximately 150-microm diameter) and veins ( approximately 250-microm diameter) were dissected from male GC-A-deficient 129sv mice or age-matched wild-type controls and mounted in a wire myograph. In the wild-type mice, ANP exhibited higher potency in the veins than in the arteries (EC(50) values wild-type mice: artery, 8 +/- 3 x 10(-9) M, n = 5 vs. vein, 6 +/- 4 x 10(-10) M, n = 5; P < 0.05). The concentration-response curve for ANP-induced vasoconstriction was also shifted leftward in denuded compared with intact arteries (EC(50) values: denuded artery: 5 +/- 3 x 10(-10) M, n = 5 vs. intact artery, 8 +/- 3 x 10(-9) M, n = 5; P < 0.05), i.e., the denuded vessels were more reactive. By contrast, ANP caused no significant change in tension from baseline in intact splenic arteries, intact splenic veins, or denuded splenic arteries derived from the GC-A-deficient mice, although these vessels did show normal concentration-dependent increases in tension to phenylephrine. We conclude that ANP causes vasoconstriction in the splenic vasculature by an endothelium-independent mechanism, mediated via guanylyl cyclase.

Myogenic responses and compliance of mesenteric and splenic vasculature in the rat

In the rat, the spleen is a major site of fluid efflux out of the blood. By contrast, the mesenteric vasculature serves as a blood reservoir. We proposed that the compliance and myogenic responses of these vascular beds would reflect their different functional demands. Mesenteric and splenic arterioles ( approximately 150-200 microm) and venules (<250 microm) from rats anesthetized with pentobarbital sodium were mounted in a pressurized myograph. Mesenteric arterial diameter decreased from 146 +/- 6 to 133 +/- 6 microm on raising intraluminal pressures from 80 to 120 mmHg. This response was enhanced in the presence of N(omega)-nitro-l-arginine methyl ester (l-NAME; 139 +/- 6 to 112 +/- 7 microm). There was no such myogenic response in the splenic arterioles, except in the presence of l-NAME (194 +/- 4 to 164 +/- 4.2 microm). We propose that, whereas mesenteric arterioles exhibit myogenic responses, this is normally masked by NO-mediated dilation in the splenic vessels. The mesenteric venules were highly distensible (active, 184 +/- 15 to 320 +/- 30.9 microm; passive in Ca(2+)-free media, 209 +/- 31 to 344 +/- 27 microm; 4-8 mmHg) compared with the splenic vessels (active, 169 +/- 11 to 184 +/- 16 microm; passive, 187 +/- 12 to 207 +/- 17 microm). We conclude that, in response to an increase in perfusion pressure, mesenteric arterial diameter would decrease to limit the changes in flow and microvascular pressure. In addition, mesenteric venous capacitance would increase. By contrast, splenic arterial diameter would increase, while there would be little change in venous diameter. This would enhance the increase in intrasplenic microvascular pressure and increase fluid extravasation.

[Comparison of methods for the identification of the most common yeasts in the clinical microbiology laboratory]

We evaluated different methods for the routine identification of medically important yeasts. A total of 150 clinical isolates: 25 C. albicans, 25 C. tropicalis, 25 C. glabrata, 25 C. parapsilosis, 8 C. guilliermondii, 11 C. krusei and 31 Cryptococcus neoformans were tested by Yeast Biochemical Card bioMerieux Vitek (YBC), CHROMagar Candida (CHR). The addition of yeast morphology in Corn Meal agar-Tween 80 (AM) to YBC and CHR was also evaluated. The reference methods used were: API 20C, germ tube formation, AM, Christensen urea and Birdseed agar. YBC identified 135 yeasts with an overall accuracy of 90%. Sensitivity (S) and specificity (E) were: 92-98% for C. albicans and C. tropicalis; 84-99% for C. papapsilosis; 100-99% for C. glabrata; 91-100% for C. krusei; 63-98% for C. guilliermondii and 90-99% for Cryptococcus neoformans, respectively. CHR identified correctly 100% for C. albicans, 92% for C. tropicalis and 91% for C. krusei. Both methods combined with AM provided 100% S and E. We found that YBC system was appropriate for identification of yeasts isolated from human sources. CHR was effective and easy to use for identification of C. albicans, C. tropicalis and C. krusei. The routine use of AM with both methods is recommended.

Effect of NOS inhibition on central response to atrial distension during pregnancy

Atrial distension increases c-fos expression in the paraventricular nucleus of virgin, but not pregnant, rats. We proposed that nitric oxide (NO), biosynthesis of which increases during pregnancy, blunts this reflex and that blocking NO biosynthesis would restore the response. Female rats were implanted with indwelling intracardiac balloons. On day 14 of pregnancy, osmotic minipumps containing either D- or N(G)-nitro-L-arginine methyl ester (L-NAME) (120 mg/2 ml at 10 microg/min) were implanted. On day 20, the rats were infused with saline (3 ml/h) with or without atrial balloon inflation (1 h). The brains were then processed for quantitation of c-fos expression. In the virgin rats, and in the pregnant rats treated with L-NAME, atrial distension significantly increased hypothalamic c-fos expression. In the pregnant animals treated with D-NAME, the response was greatly attenuated. NO had no effect on the increase in atrial receptor afferent discharge (single-fiber recordings) elicited by atrial distension. We conclude that, during pregnancy, NO attenuates central processing of the reflex response to atrial distension but does not alter the transducer properties of the volume receptors.

[False-positive cultures due to cross contamination in tuberculosis laboratories]

Fifteen episodes of Mycobacterium tuberculosis laboratory cross-contamination suspected between 1996 and 2001 at 6 laboratories in Buenos Aires City and suburbs were investigated by IS6110 RFLP. Thirteen episodes were confirmed. Even though BACTEC 460 produced the highest number of confirmed episodes in a single laboratory, the most extended one occurred while employing conventional culture procedures in solid medium. The double repetitive element-polymerase chain reaction (DRE-PCR) was applied to 8 of these episodes and produced concordant results with those of the RFLP. The DRE-PCR appears to be a valuable tool for the prompt identification of false positive cultures. The timely rectification of defects in laboratory protocols can avert false diagnoses of tuberculosis and unnecessary prolonged treatments.