Biodistribution of 18F- and 125I-labeled anti-Tac disulfide-stabilized Fv fragments in nude mice with interleukin 2 alpha receptor-positive tumor xenografts

We evaluated the biodistribution, pharmacokinetics, and generation of catabolites of an 18F- and 125I-labeled anti-Tac disulfide-stabilized Fv fragment (dsFv) in tumor-bearing nude mice. This dsFv is genetically engineered from a murine monoclonal antibody that recognizes the alpha subunit of the interleukin 2 (IL-2 alpha) receptor. Labeling was performed with 18F using N-succinimidyl 4-([18F]fluoromethyl)benzoate or with 125I using the Iodo-Gen method. The immunoreactivities of the radiolabeled anti-Tac dsFv were > 82%. The biodistribution was evaluated (at 15, 45, and 90 min and 6 h) in athymic nude mice (approximately five/group) bearing s.c. tumor xenografts. Cell line A431 served as the IL-2 receptor-negative control tumor, whereas the ATAC4 cell line served as our IL-2 receptor-positive tumor. Animals received injections of 18F-labeled anti-Tac dsFv (0.7-1.4 megabecquerels/1.5-3 micrograms) and 125I-labeled anti-Tac dsFv (0.1-0.4 megabecquerels/0.9-1 microgram). Blood clearance for both preparations was rapid, with < 10% retained in the blood by 15 min. Maximum accumulation in ATAC4 tumors occurred between 45 and 90 min and peaked at a mean of 4.2% injected dose/g (18F) and 5.6% of injected dose/g (125I). At 6 h, the ATAC4 tumors contained 11 times more 18F and 3 times more 125I than did the A431 tumors. The ATAC4 tumor:blood ratios for the 18F and 125I were > 12:1 and > 1.4:1 at 6 h, respectively, whereas the ratios for the antigen-negative A431 tumor were less than 1. The kidneys were the major route of elimination. Catabolites appeared quickly and were identified as [125I]iodide and predominantly N-epsilon-[18F]4-fluoromethylbenzoyl(alpha-N-acetyl) lysine. This is the first study to evaluate the biodistribution of an 18F-labeled Fv fragment in vitro and in vivo. In vivo, the dsFv was taken up rapidly by the kidneys, producing lysine-containing catabolites for 18F-labeled dsFv and [125I]iodide for 125I-labeled dsFv.

Inhibition of clinical human immunodeficiency virus (HIV) type 1 isolates in primary CD4+ T lymphocytes by retroviral vectors expressing anti-HIV genes

Gene therapy may be of benefit in human immunodeficiency virus type 1 (HIV-1)-infected individuals by virtue of its ability to inhibit virus replication and prevent viral gene expression. It is not known whether anti-HIV-1 gene therapy strategies based on antisense or transdominant HIV-1 mutant proteins can inhibit the replication and expression of clinical HIV-1 isolates in primary CD4+ T lymphocytes. We therefore transduced CD4+ T lymphocytes from uninfected individuals with retroviral vectors expressing either HIV-1-specific antisense-TAR or antisense-Tat/Rev RNA, transdominant HIV-1 Rev protein, and a combination of antisense-TAR and transdominant Rev. The engineered CD4+ T lymphocytes were then infected with four different clinical HIV-1 isolates. We found that replication of all HIV-1 isolates was inhibited by all the anti-HIV vectors tested. Greater inhibition of HIV-1 was observed with transdominant Rev than with antisense RNA. We hereby demonstrated effective protection by antisense RNA or transdominant mutant proteins against HIV-1 infection in primary CD4+ T lymphocytes using clinical HIV-1 isolates, and this represents an essential step toward clinical anti-HIV-1 gene therapy.

Microangiopathic hemolytic anemia as an initial presentation of metastatic cancer of unknown primary origin

Microangiopathic hemolytic anemia (MAHA) is a well-documented but rare complication of disseminated cancer; it usually occurs in the late or terminal stage of cancer. We describe a case of metastatic carcinoma of unknown origin in which MAHA was the initial presentation. A 36-year-old woman came to our hospital with lower back pain and progressive exertional dyspnea for 8 weeks. Hemolytic anemia, thrombocytopenia, and leukoerythroblastosis were found on admission. The peripheral blood smear revealed polychromasia, poikilocytosis, and many schistocytes. Bone marrow biopsy disclosed metastatic carcinoma. After careful workup, we failed to find the primary site of cancer. The anemia and thrombocytopenia responded dramatically to combination chemotherapy with 5-fluorouracil, mitomycin C, and cisplatin. This case indicates that metastatic carcinoma should be included in the differential diagnosis in previously healthy patients with MAHA.

Cisplatin and 5-fluorouracil as neoadjuvant chemotherapy: predicting response in head and neck squamous cell cancer

In order to prospectively evaluate the efficacy, toxicity and predictive factors of response to neoadjuvant chemotherapy, a total of 120 patients with head and neck squamous cell cancer diagnosed from January 1992 to November 1993 were enrolled in this study. There were 118 male and 2 female patients, with a median age of 51 years (range 30-74 years). The primary sites were the oral cavity (77), oropharynx (15), hypopharynx (25) and larynx (3). Betel quid chewing was habitual in 91% of patients. All patients were previously untreated, and 94% had stage III or IV disease. Chemotherapy was given in two or three courses to 96 patients who were then assessed for response rate and predictive factors. The chemotherapy regimen consisted of cisplatin 100 mg/m2/day on day 1 and 5-fluorouracil (5-FU) 1 g/m2/day intravenous infusion continuously for 4 to 5 days for 4 weeks. The overall chemotherapy response rate was 56%, with a 3% complete response. By univariate analysis, both the T-stage and tumor volume were significant for predicting the response of the primary site. The age, histologic differentiation, tumor location and N-stage were unpredictive for response. The nodal response (43%) was less than that of the primary site (68%). By multivariate analysis, only the tumor volume (> or = 50 cm3) and the presence of nodal metastases were predictive for the combined TN response. Based on the World Health Organization toxicity criteria, 49 patients experienced grade 3 to 4 mucositis, and 24 patients had grade 3 to 4 vomiting.(ABSTRACT TRUNCATED AT 250 WORDS)

An autoregulated dual-function antitat gene for human immunodeficiency virus type 1 gene therapy

One approach to gene therapy for AIDS is to block the replication of human immunodeficiency virus type 1 (HIV-1) by inhibiting that tat gene, whose product activates the expression of all HIV-1 genes. To accomplish this, we constructed an antitat gene expressing an RNA with dual (polymeric TAR and antisense-tat) function in an attempt to both sequester Tat protein and block its translation from mRNA. A minigene consisting of the antitat gene driven by the HIV-1 long terminal repeat was inserted into a double-copy retrovirus vector, such that antitat expression would be upregulated only in HIV-1-infected cells. After transduction of a T-lymphocytic cell line (Molt-3) the antitat gene inhibited HIV-1 replication. This inhibition was inversely correlated with the virus infections dose. Virus replication was also inhibited for 5 months in two different T-cell lines after they had been infected at a high multiplicity of infection, suggesting that the antitat gene may be effective over long periods. Importantly, antitat blocked the replication and the cytopathic effect of HIV-1 in human peripheral blood mononuclear cells and led to as much as 4,000-fold inhibition of the replication of an HIV-1 field isolate as well as HIV-1 prototypes maintained in culture. These results suggest that antitat gene therapy has potential use for blocking HIV-1 replication in infected individuals.

Inhibition of human immunodeficiency virus type-1 by retroviral vectors expressing antisense-TAR

The human immunodeficiency virus type-1 (HIV-1) Tat activation response (TAR) region is essential for Tat-mediated trans-activation of the HIV-1 long terminal repeat (LTR). The TAR element is present on the 5' and 3' ends of all HIV-1 transcripts and is relatively conserved among different HIV-1 isolates. These properties make it an attractive target for anti-HIV-1 gene therapy strategies. We have constructed a Moloney murine leukemia-based retroviral vector that expresses a chimeric tRNA(iMet)-antisense TAR fusion transcript complementary to the HIV-1 TAR region. The potential of this anti-TAR retroviral vector to inhibit HIV-1 was initially tested by transient transfections with an HIV-1-LTR-Tat expression plasmid into HeLa-CAT cells. Anti-TAR inhibited Tat-mediated HIV-1 LTR-driven CAT reporter gene expression in a dose-dependent fashion. The antisense-TAR vector was then used to transduce the human SupT1 T cell line. Cotransfection of these SupT1 cells with a Tat expression plasmid plus an HIV-1 LTR-CAT reporter plasmid resulted in decreased CAT gene expression in comparison to control transduced SupT1 cells. The antisense-TAR engineered SupT1 cell line was then challenged with HIV-1MN.HIV-1 viral production was inhibited in SupT1 cells transduced with the antisense-TAR retroviral vector. Greater inhibition of HIV-1 was observed with antisense-TAR as compared to antisense-Tat expressing retroviral vector. These observations suggest that antisense-TAR retroviral vectors are potentially useful for clinical anti-HIV-1 gene therapy.

Synergy between basic fibroblast growth factor and HIV-1 Tat protein in induction of Kaposi's sarcoma

Basic fibroblast growth factor (bFGF) and human immunodeficiency virus type 1 (HIV-1) Tat protein synergize in inducing angiogenic Kaposi's sarcoma-like lesions in mice. Synergy is due to Tat, which enhances endothelial cell growth and type-IV collagenase expression in response to bFGF mimicking extracellular matrix proteins. The bFGF, extracellular Tat and Tat receptors are present in HIV-1-associated KS, which may explain the higher frequency and aggressiveness of this form compared to classical Kaposi's sarcoma where only bFGF is present.

Block of HIV-1 infection by a combination of antisense tat RNA and TAR decoys: a strategy for control of HIV-1

The tat gene product (Tat) of HIV-1 is an early regulatory protein necessary for viral gene expression and replication. Tat may also play a role as an extracellular protein in both HIV-1 replication and AIDS-associated disorders such as Kaposi's sarcoma. Thus, Tat represents a good target for gene therapy against AIDS. Here we show that when vectors expressing antisense tat RNA are transiently transfected into CD4+ cells, they block about 70% of HIV-1 replication and inhibit the rescue of Tat-defective HIV-1 proviruses by inhibition of Tat protein expression and consequent lack of transcriptional activation of the HIV-promoter. However, antisense tat vectors cannot block the activity of extracellular Tat protein. Another tat inhibitory construct (poly-Tat-activation response; TAR) previously suggested to inhibit HIV-1 transactivation by sequestering the Tat protein, inhibited the activity of extracellular Tat, but like antisense tat RNA did not completely block viral gene expression and replication. These results suggested that one mode of inhibition is not sufficient to block Tat function. However, when the antisense tat and the poly-TAR constructs were combined HIV-1 gene expression was completely blocked (94-98%), suggesting that a combination of inhibitory genes blocking Tat by sequential steps may be a better approach for AIDS gene therapy.

Correlations between flow resistance and geometry in a model of the human nose

The relationship between the pressure losses within the nasal airways and nasal geometry were studied in a 3:1 scale model. The geometry of the model was based on magnetic resonance images of the skull of a healthy male subject. Pressure measurements, flow visualization, and hot-wire anemometry studies were performed at flow rates that, in vivo, corresponded to flows of between 0.05 and 1.50 l/s. The influence of nasal congestion and the collapse of the external nares were examined by using modeling clay to simulate local constrictions in the cross section. A dimensionless analysis of the pressure losses within three sections of the airway revealed the influence of various anatomic dimensions on nasal resistance. The region of the exterior nose behaves as a contraction-expansion nozzle in which the pressure losses are a function of the smallest cross-sectional area. Losses in the interior nose resemble those associated with channel flow. The nasopharynx is modeled as a sharp bend in a circular duct. Good correspondence was found between the predicted and actual pressure losses in the model under conditions that stimulated local obstructions and congestion.

Directionally Aligned Helical Peptides on Surfaces

Directionally oriented peptide layers 1000 angstroms thick were constructed by polymerization on gold and indium-tin-oxide glass. A key feature is the use of an appropriately functionalized surface on which the initiation sites for polymerization are spaced at distances consistent with the helical diameter of the peptide. Completely helical polyalanine and polyphenylalanine layers have been constructed. The helicity of the polyalanine layer was completely retained after heating at 180 degrees C for 7 days.

Effects of the human immunodeficiency virus type 1 Tat protein on the expression of inflammatory cytokines

Increased levels of inflammatory cytokines, including tumor necrosis factor (TNF), interleukin-1 (IL-1), and IL-6, have been detected in specimens from human immunodeficiency virus type 1 (HIV-1)-infected individuals. Here we demonstrate that HIV-1 activates the expression of TNF but not of IL-1 and IL-6 in acutely and chronically infected T cells. The increase in TNF gene expression is due to activation of the TNF promoter by the viral gene product Tat. Transactivation of TNF gene expression requires the product of the first exon of the tat gene and is cell type independent. T cells chronically infected with pol-defective HIV-1 provirus constitutively express both Tat and TNF at levels significantly higher (fivefold) than those seen in control cells, and treatment with phorbol myristate acetate greatly enhances Tat expression and TNF production. As TNF can increase the production of IL-1 and IL-6 and these inflammatory cytokines all enhance HIV-1 gene expression and affect the immune, vascular, and central nervous systems, the activation of TNF by Tat may be part of a complex pathway in which HIV-1 uses viral products and host factors to increase its own expression and infectivity and to induce disease.

Prognosis of thymic carcinoma: analysis of 16 cases

Primary thymic carcinoma is a rare malignant neoplasm which arises from the thymic epithelium. Between May 1982 and September 1990, 16 patients with thymic carcinomas, diagnosed at Chang Gung Memorial Hospital, were reviewed. Their ages ranged from 19 to 75 years, with a median of 40 years. Males predominated (male to female ratio was 11:5). The most common presenting symptoms were chest pain, cough, body weight loss and dyspnea. No paraneoplastic syndromes were seen. Chest roentgenograms of 15 patients revealed a mediastinal mass, but a definitive diagnosis could not be made until surgery. Adjacent mediastinal tissues were invaded, or adhered to, by all the tumors. Six distinct histologic types were found, squamous cell carcinoma being the most common (seven cases). The primary treatment of surgical resection was attempted in 14 patients, but only in five cases could the tumors be completely resected; two had a biopsy only. Radiotherapy, with or without chemotherapy, given postoperatively, achieved additional local control in seven of the nine partially resected patients (77%). Distant metastasis occurred in nine of 16 patients (56%). Lymph nodes, bone and lung were the most common metastatic sites. Chemotherapy with cisplatin and/or adriamycin-based regimens was given to patients who had distant metastasis, but the responses were unsatisfactory. The overall survival at one, three and five years was 88%, 51% and 31%, respectively. The median survival was 30 months. The median survival of patients with pure squamous cell carcinoma (> 49 months) was superior to that of patients with other histologic types (18 months; p < 0.01).

[The coexistence of vesicoureteral reflux and ureteropelvic junction obstruction in children]

From January 1982 to December 1990, there were 229 cases with 337 ureters having vesicoureteral reflux (VUR). Thirteen of them (3.86%) were also found to have ureteropelvic junction (UPJ) obstruction in the same ureter. They were categorized into three groups based on the therapeutic implications. Group 1 (two ureters) underwent pyeloplasty. Group 2 (two ureters) received both pyeloplasty and reimplantation. The remaining nine ureters having VUR and pseudo-obstruction fell into group 3, and two of them became true UPJ obstruction eventually. We stressed the importance of evaluating upper urinary tract in all refluxed ureters with inappropriately dilated renal pelvis. By doing that we can avoid unnecessary surgery and prevent complications from wrong sequence of operation to a least extent.

Steady and oscillatory transnasal pressure-flow relationships in healthy adults

The influence of flow characteristics and gas physical properties on nasal resistance (NR) is difficult to ascertain with traditional rhinomanometric methods because the respiratory airflows used in these methods are largely uncontrolled. As an alternative, we used a novel method of rhinomanometry in which an externally generated flow is passed through the nasal passage via a mouthpiece. The transnasal pressure-flow relationships for both quasi-steady and oscillating flows and with different gases were obtained in five healthy adults with this method. For quasi-steady nasal flows the dimensionless pressure losses were largely independent of physical properties of the gas and a function of the Reynolds number (Re) of the flow. Values of NR for quasi-steady flows were largely independent of flow direction for Re up to roughly 3,000 in all five subjects and for Re up to roughly 19,000 in two of the five subjects. Airway collapse occurred in two subjects at Re greater than 3,000, suggesting that the nonrigid segments of the nasal passage contribute to the intersubject variations in NR at high flow rates. Pressure losses associated with oscillating flows measured at frequencies between 1 and 16 Hz were similar to steady flow losses provided that Re was less than roughly 3,000. For Re greater than 3,000 the oscillating flow resistances were affected by the phasic redistribution of flow into compliant segments of the nasal passage. These results indicate that, for flow rates and harmonic frequencies associated with breathing at rest, the nasal passage behaves as a rigid rough-walled pipe in which pressure losses are largely determined by forces relating to viscous friction and convective accelerations.

Single-incision nephroureterectomy combined with transurethral incision of bladder cuff for renal pelvic tumor

With the extended use of transurethral endoscopic surgery, we modified the conventional nephroureterectomy that usually requires either a very long incision or two separate shorter incisions. From August 1983 to October 1988, 13 cases of renal pelvic tumor in this hospital were treated single-incision nephroureterectomy combined with transurethral incision of the bladder cuff. The advantages of this technique were less surgical time and a decrease in postoperative wound pain. There were no significant complications or local recurrence noted in this series. The proposed indications were urothelial tumors in the renal pelvis and upper ureter without demonstrable metastases. Tumors of an uncertain cell type preoperatively are especially indicated. The details of this technique are described.

A new method to measure nasal impedance in spontaneously breathing adults

As an alternative to standard rhinomanometric methods, we applied forced oscillations at the mouth in five normal subjects and determined their nasal impedance with a novel method involving flow subtraction. Pressure oscillations of constant amplitude were applied at the mouth of a subject both when the nostrils were open and when they were closed with a noseclip. The airflows measured under the two conditions were subtracted to yield the oscillating nasal airflow at the imposed pressure. The resultant pressure-flow relation defined the nasal impedance of the subject. For frequencies between 3 and 15 Hz, the transnasal pressure-flow relation was well described by a linear lumped parameter model consisting of a resistive and inertial element. Nasal resistance obtained with flow subtraction did not differ significantly from control measurements obtained while the subjects performed the Valsalva maneuver. In contrast, nasal inertance obtained with flow subtraction was approximately twice that obtained with the Valsalva method. The difference between inertances may reflect structural changes in nasopharyngeal dimensions that occur with the Valsalva maneuver. We conclude that the mechanical impedance of the nasal passage may be determined during spontaneous breathing from the response to imposed forced oscillations at the mouth. The noninvasive nature of this method suggests that it may be simpler to implement than traditional rhinomanometric methods.

A primary mucinous cystoadenocarcinoma of the retroperitoneum

A case of primary retroperitoneal mucinous cystoadenocarcinoma of the ovarian type in the presence of normal ovaries is reported. The histogenesis of this rare tumor has been uncertain. Special immunohistochemical stains done on our specimen show that the histogenesis of this tumor is most likely from mucinous metaplasia of coelomic mesothelium. Three cases of primary retroperitoneal mucinous cystoadenocarcinoma of the ovarian type have previously been reported in the English literature and are reviewed.

Resin-bonded fixed partial dentures: a recall study

A clinical recall program was initiated at the University of Minnesota to evaluate the longevity and factors affecting longevity of resin-bonded fixed partial dentures (FPDs). Of the 49 resin-bonded FPDs evaluated in the clinic, 43 were acid-etched metal, resin-bonded FPDs, four were combinations of resin-bonded and conventional FPDs, and two were composite resin pontics. None of the combination FPDs and one of the two composite resin pontics were judged as failed at the examination. Of the 43 acid-etched metal resin-bonded FPDs, 15 were found to be debonded (failure rate = 34.9%). The average length of service for the 43 FPDs was 47.3 months. The average time of placement to debondment was 33 months for the 15 debonded FPDs. The failure rate for maxillary FPDs and FPDs with two retainers were significantly lower than the failure rate for mandibular FPDs and FPDs with more than two retainers (p greater than 0.05). The clinical significance of the present study was discussed.

Pulsatile pulmonary microvascular pressure measured with vascular occlusion techniques

The periodic variations of the pulmonary microvascular pressure during pulsatile perfusion were studied in isolated left lower lobes of canine lungs by the arterial occlusion (AO) and double occlusion (DO) techniques. Sixteen AO and eight DO maneuvers evenly distributed within the pump cycle were performed for each of four frequencies: 36, 54, 72, and 90 beats/min. Nearly identical microvascular pressure contours were reconstructed from the AO and DO maneuvers by relocating the measured occlusion pressures in time. These contours lagged behind the pulmonary arterial pressure waveform. Their amplitude decreased from 25 to 14% of the arterial pulse pressure as the pump frequency was increased from 36 to 90 beats/min. The modulus of the pressure transfer function at the site of arterial occlusion decreased as the frequency increased. The phase was negative for all frequencies and it approached -90 degrees for the higher frequencies. Vasoconstriction induced by serotonin resulted in an increase of the magnitude of the AO pressure contour that was nearly proportional to the increase of the pulmonary arterial pulse pressure. In contrast, elevation of the lobar venous pressure to 10 mmHg increased the amplitude of the AO pressure contour, whereas it slightly decreased the pulmonary arterial pulse pressure. These experiments demonstrate that the AO and DO pressures fluctuate markedly during pulsatile perfusion. Their oscillations would be indicative of the pulsatility in the pulmonary microvascular bed.

A forced perturbation method of assessing pulmonary mechanical function in intubated infants

Short pulses in airway pressure were used to assess the pulmonary mechanical function of nine infants suffering acute respiratory distress syndrome or bronchopulmonary dysplasia. All patients were intubated, spontaneously breathing, and mechanically ventilated at the time they were examined. The endotracheal tube was disconnected from the ventilator and connected to a mechanical oscillator that produced brief pulses in airway pressure at a rate of two pulses/s. These pulses were applied to the infants airway for 20-30 s, at which time the infant was replaced on the ventilator. The mean airway pressure during the procedure was maintained at the level of the positive and expiratory pressure that was set on the ventilator. Two classes of patients were identified from the pulse response primarily by the presence or absence of a local resonance in the impedance spectra. Similar results were obtained in five other patients who were examined with zero mean airway pressure, suggesting that the pulse response is little influenced by changes in mean lung volume or total lung compliance. Patient classification appeared related to the duration of ventilation therapy and the transition from one class to another was consistent with the development of high peripheral airway resistance and significant volume shunting in the central airways. These results suggest that brief pulses in airway pressure can be used to detect changes in the pulmonary mechanical function of preterm infants that result from long-term ventilation therapy.

Pulmonary lobar vascular resistances during constant and pulsatile flows

We measured arterial and venous occlusion pressure profiles in left lower lobes of dog lungs perfused in constant flow and pulsatile flow. Initially, pulmonary arterial pressure, flow rate, and venous pressure were recorded during a series of inflow and outflow occlusions effected during constant flow perfusion. The perfusion was then made pulsatile and while keeping the same flow rate, a second series of vascular occlusions was performed. The arterial occlusion pressures measured with the two modes of perfusion were similar. During pulsatile perfusion, the variation in arterial pressure following an arterial occlusion varied with the timing of occlusion in the pressure cycle. The arterial pressure drop could be recovered by selecting the time-averaged pulmonary arterial pressure as the upstream pressure. During both types of perfusion, the venous occlusion curves were similar. The arterial and venous pressure drops were approximately 4.8 mm Hg and 4.2 mm Hg, respectively. We concluded that the longitudinal distribution of pulmonary vascular pressures can be inferred from occlusion measurements obtained in pulsatile flow.

Lung and chest wall mechanics in rabbits during high-frequency body-surface oscillation

In eight anesthetized and tracheotomized rabbits, we studied the transfer impedances of the respiratory system during normocapnic ventilation by high-frequency body-surface oscillation from 3 to 15 Hz. The total respiratory impedance was partitioned into pulmonary and chest wall impedances to characterize the oscillatory mechanical properties of each component. The pulmonary and chest wall resistances were not frequency dependent in the 3- to 15-Hz range. The mean pulmonary resistance was 13.8 +/- 3.2 (SD) cmH2O.l-1.s, although the mean chest wall resistance was 8.6 +/- 2.0 cmH2O.l-1.s. The pulmonary elastance and inertance were 0.247 +/- 0.095 cmH2O/ml and 0.103 +/- 0.033 cmH2O.l-1.s2, respectively. The chest wall elastance and inertance were 0.533 +/- 0.136 cmH2O/ml and 0.041 +/- 0.063 cmH2O.l-1.s2, respectively. With a linear mechanical behavior, the transpulmonary pressure oscillations required to ventilate these tracheotomized animals were at their minimal value at 3 Hz. As the ventilatory frequency was increased beyond 6-9 Hz, both the minute ventilation necessary to maintain normocapnia and the pulmonary impedance increased. These data suggest that ventilation by body-surface oscillation is better suited for relatively moderate frequencies in rabbits with normal lungs.

Pulmonary vascular impedance in microembolic pulmonary hypertension: effects of synchronous high-frequency jet ventilation

Increased intrathoracic pressure (ITP) during conventional mechanical ventilation may interfere with the adaptation of right ventricular function to pulmonary hypertension. We studied the effects of synchronous cardiac cycle-specific high frequency jet ventilation (HFJV) in 10 anesthetized dogs before and after embolization of the pulmonary artery with 150-200 microns glass beads. The delivery of the jet was synchronized with early systole, late systole, early diastole and late diastole of the cardiac cycle. Right and left ventricular pressures (Prv and Plv) and pulmonary arterial pressures (Ppa) were measured by transducer-tipped catheters and pulmonary blood flow by an ultrasonic flow probe. Right ventricular end-systolic and end-diastolic volumes (rvESV and rvEDV) were estimated from the thermodilution curve obtained with a Swan-Ganz catheter equipped with a fast response thermistor. Pulmonary hypertension caused significant increases in heart rate (89 +/- 7 to 152 +/- 8 beats/min), rvEDV (80 +/- 7 to 131 +/- 23 ml), diastolic transmural Prv (2 +/- 1 to 5 +/- 1 mm Hg), and rv peak dP/dt (652 +/- 151 to 1035 +/- 160 mm Hg/s). The spectrum of pulmonary vascular input impedance was displaced towards higher frequencies, input resistance was increased and characteristic impedance decreased. The latter change contributed to a relative decrease in the pulsatile component of right ventricular power output. Cardiac output remained unchanged (2.1 +/- 0.2 to 1.9 +/- 0.1 L/min, P NS). Non of these measurements was affected by the timing of the increase in ITP to specific instants in the cardiac cycle compared to apneic periods at any level of pulmonary hypertension. We conclude that in acute microembolic pulmonary hypertension 1 degree a decrease in characteristic impedance contributes to the adaptation of right ventricular function to increased afterload and 2 degrees synchronous cardiac cycle-specific HFJV has no detectable hemodynamic effect.

Vasectomy and non-fatal acute myocardial infarction: a hospital-based case-control study in Seoul, Korea

One hundred and sixty-three Korean men aged 35-64 who were admitted to a university-affiliated hospital diagnosed for the first time with acute myocardial infarction (AMI) were compared with 326 matched non-AMI patients hospitalized with a diagnosis considered unrelated to vasectomy. When other potentially confounding variables were controlled for, vasectomized men were found to be 2.6 times (adjusted odds ratio) more likely to have had an AMI as compared to the non-vasectomized men (95% CL: 1.1, 6.1). The adjusted odds ratio of AMI for subjects having had a vasectomy less than or equal to 9 years ago was the same as those who had a vasectomy greater than or equal to 15 years (OR = 2.5), although those who had had a vasectomy 10-14 years ago were associated with a higher odds ratio of 4.2. Among those subjects with vasectomies who were also cigarette-smokers and/or hypertensive, the risk of development of AMI increased multiplicatively compared with those with none of these conditions. We suspect that our finding of this positive association may be spurious due to possible bias introduced during selection of controls and during the process of data collection. Cancer patients may have been less likely to undergo an elective surgical procedure such as vasectomy prior to the admission. When multivariate analysis included only controls who were non-cancer patients (N = 241 controls), the adjusted odds ratio between vasectomy and hospitalization for AMI was reduced to 2.1, (95% CL: 0.8, 5.7), which is no longer statistically significant. When the analysis was further limited to only those control subjects admitted with a diagnosis of digestive system problems, the adjusted odds ratio was reduced to close to unity (1.1). Recognizing the importance of the study topic and the fact that all previous epidemiological studies showed no association between vasectomy and cardiovascular diseases, we urge further studies. A historical cohort study in the Korean setting is considered feasible and is recommended.

Analysis of pulmonary arterial pressure profile after occlusion of pulsatile blood flow

In isolated canine lung lobes perfused with a pulsatile pump, arterial occlusions were performed and the postocclusion arterial pressure profiles were analyzed to estimate the pulmonary capillary pressure. A solenoid valve interposed between the pump and the lobar artery was used to perform arterial occlusions at several instants equally distributed within a pressure cycle. Double occlusions were also accomplished by simultaneously activating the solenoid valve and clamping the venous outflow of the lung lobe. To analyze an arterial occlusion pressure profile, we computed the best monoexponential fit of the pressure decay over a short period of time after the occlusion maneuvers. Two estimates of the capillary pressure were derived from this analysis: 1) the extrapolation of the exponential fit to the instant of occlusion, and 2) the point at which the recorded pressure decay curve merges with the exponential fit. The pressures thus determined were compared with the double occlusion pressure that provided an independent estimate of the pulmonary capillary pressure. Our results show that, under a wide range of conditions, the estimates of the capillary pressure obtained from the arterial occlusion data are nearly equal to the double occlusion pressures. Additionally, we estimated the capillary pressure variations within a pressure cycle by examining the occlusion pressures sampled at different instants of the cycle. The pulsatility of the pulmonary microvascular pressure varied with the pump frequency as well as the state of arterial and venous vasoaction. These variations are consistent with the representation of the lung vasculature as a low-pass filter.