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Biomedical subjects

D J Lang

Publications and source records attributed to D J Lang.

At least 37 records · Page 2Linked to original sources
PubMed1995

Position of epicardial patch electrodes for implantable defibrillation significantly affects shock strength requirements.

OBJECTIVE: To assess the impact of epicardial patch electrode position on internal defibrillation efficacy. METHODS: Two mesh patch electrodes (13 cm2) were positioned on the epicardium of acute, isoflurane-anesthetized pigs (n = 7, 40-47 kg). Defibrillation efficacy was determined for three different patch positions: P1 = anterior-basal right ventricle (RV) and lateral-apical left ventricle (LV); P2 = lateral RV and lateral LV; and P3 = anterior-basal septal region and posterior-apical septal region. To quantify defibrillation efficacy, single capacitor discharge, fixed-tilt (68%) biphasic waveforms were delivered to the heart 10 seconds after initiation of ventricular fibrillation. Initial shock intensities were selected using an up/down protocol. Conversion data were used to construct sigmoidal curves relating probability of defibrillation to energy delivered, peak voltage, and peak current in each animal. RESULTS: Mean peak voltage and current at 50% defibrillation probability were 40% higher for P2 than they were for either P1 or P3 (p < 0.05). Similarly, mean energy delivered was 75% higher for P2. In this pig model, position of epicardial patch electrodes affects defibrillation efficacy. CONCLUSION: Apical-to-basal shock vectors (P1 and P3) yielded significantly lower defibrillation shock strength requirements than did a lateral-wall-to-lateral-wall vector (P2), which was perpendicular to the intraventricular septum. These data may help explain the disparity in defibrillation thresholds observed in the human population of patients undergoing implantable cardioverter defibrillator testing with epicardial patch electrodes.

Animals↗
PubMed1994

Comparative study of the safety and efficacy of clarithromycin and amoxicillin-clavulanate in the treatment of acute otitis media in children.

The safety and efficacy of clarithromycin was compared with those of amoxicillin-potassium calvulanate for the treatment of acute otitis media in children. In a multicenter, randomized, investigator-blinded trial, 180 patients (6 months to 12 years of age) with acute otitis media were allocated to receive either clarithromycin, 15 mg/kg in two divided doses (n = 90), or amoxicillin-clavulanate, 40 mg/kg in three divided doses (n = 90), for 10 days. Middle ear samples were obtained by tympanocentesis from 175 of 180 patients. Pathogens were isolated from 137 samples (76%). Eighty-six patients in each treatment group were considered for efficacy analysis. Clinical cure or improvement was achieved within 4 days after treatment in 80 (93%) of 86 patients receiving clarithromycin and in 82 (95%) of 86 patients receiving amoxicillin-clavulanate. Recurrence of infection was observed between 5 and 35 days after treatment in 9 (11%) of 80 patients in the clarithromycin group and in 8 (10%) of 82 patients in the amoxicillin-clavulanate group. Middle ear effusion was found with similar frequency at the end of therapy and at follow-up visits in both treatment groups. Mild gastrointestinal signs and symptoms, the most common side effects, were noted in 20% and 52% of patients in the clarithromycin group and the amoxicillin-clavulanate group, respectively (p < 0.001). We conclude that clarithromycin is a safe and effective antimicrobial agent for the treatment of acute otitis media in children.

Acute Disease↗
PubMed1994

Comparison of plasma PCR and bronchoalveolar lavage fluid culture for detection of cytomegalovirus infection in adult bone marrow transplant recipients.

Plasma PCR for human cytomegalovirus (CMV) DNA was compared with bronchoalveolar lavage (BAL) fluid culture as an indicator for disseminated CMV infection. Thirteen (32.5%) of 40 consecutive bone marrow transplant (BMT) recipients were BAL fluid culture positive for CMV on day 35 post-BMT, and 9 (69%) of the 13 had positive plasma PCRs between days 28 and 49. Of the 27 with negative BAL fluid cultures, 2 (7%) had positive plasma PCRs (P < 0.001). Plasma CMV DNA in BMT recipients is a useful clinical marker for serious infection.

Adult↗
PubMed1990

Cell therapy in children with Down syndrome: a retrospective study.

Cell therapy, the administration of freeze-dried or lyophilized cells derived from fetal tissue of animals, has been suggested and accepted by some parents as a treatment for Down syndrome. Such therapy regimens have been purported to ameliorate dysmorphic features and to result in improvement in IQ, motor skills, social behavior, height, language, and memory. Interest in this therapy continues despite a lack of empirical support for its use and its illegality in the United States. In this study, 190 subjects of whom 21 had received cell therapy (from sources external to this study) were studied for 18 variables in the areas of growth, motor development, cognitive development, and adaptive/social status. Comparing the cell-treated group with a control group matched for sex, age, socioeconomic status, and cardiac history showed no statistically significant differences for any of the developmental or growth variables measured. These findings fail to support continued claims of improved functioning following cell therapy in persons with Down syndrome.

Adolescent↗
PubMed1989

Dilator response of rat mesenteric arcading arterioles to increased blood flow velocity.

Arcading arterioles (average diam 68 microns ID) connecting adjacent triangular vascular sectors in the rat mesentery were examined in vivo for the presence of flow-dependent vasodilation. When a feed artery to one of these sectors was occluded, the affected sector was supplied by collateral flow through the arcading arteriole, and red cell velocity in the arteriole increased by 10-66 mm/s. The velocity increase was followed (with an average delay of 7.7 s) by dilation of the arcading arteriole, which averaged 68%. The dilation was closely correlated with red cell velocity (r = 0.96), volume flow (r = 0.96), and wall shear rate (r = 0.89). The dilation was sustained for the duration of increased velocity (1-10 min) and was not affected when direction of flow in the arteriole was reversed. The flow-induced dilation was equal to the maximal dilation attained with topically applied papaverine. Dilation of the arcading arteriole could be almost completely abolished if the arteriole was also occluded during occlusion of a feed artery. These observations indicate that a potent flow-dependent dilator mechanism is present in arcading arterioles of rat mesentery and may play an important role in local regulation.

Animals↗
PubMed1989

Seroepidemiologic studies of cytomegalovirus and Epstein-Barr virus infections in relation to human immunodeficiency virus type 1 infection in selected recipient populations. Transfusion Safety Study Group.

Antibodies to human cytomegalovirus (CMV) and Epstein-Barr virus (EBV) were evaluated among 1,171 persons with and without antibodies to human immunodeficiency virus type 1 (anti-HIV-1). These included 97 blood donors, 577 persons given blood components or products, and 497 controls. A significantly higher proportion of anti-HIV-1 positive than -negative donors were anti-CMV-positive, a finding associated with homosexual contact among some of the former. Among subjects with treated clotting disorders, there was no difference in prevalence of anti-CMV or anti-EBV between anti-HIV-1-positive and -negative persons. The prevalence of antibodies to EBV early antigens showed no relationship to anti-HIV-1 status. Anti-CMV positivity in anti-HIV-1-negative donors was associated with an increase in mean CD8 counts and lower mean CD4/CD8 ratio. Anti-CMV and anti-EBV positivity in anti-HIV-1-positive subjects with treated clotting disorders was not associated with a lower CD4 or higher CD8 count than HIV-1 infection alone. Subjects who developed AIDS after enrollment had no significant difference in median time from entry to diagnosis when analyzed by serologic evidence of CMV and EBV antibody status at entry, and a few subjects had AIDS at entry without serologic evidence of prior CMV or EBV infection. The overall results are consistent with acquisition and progression of HIV-1 independently of coincident CMV or EBV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Elevated ambient oxygen does not affect autoregulation in cat mesentery.

The purpose of this study was to determine whether oxygen plays a role in the autoregulation of blood flow in the isolated mesentery of the cat. Arteriolar diameter and red cell velocity were measured at normal arterial pressure and during 2 min of pressure reduction to 80 and 40 mmHg under ambient levels of 0, 10, and 20% oxygen in nitrogen. Autoregulatory responses during pressure reductions to 80 and 40 mmHg were not significantly different under 0% oxygen compared with those under 10 or 20% oxygen. Also, no significant difference was found in the control state between the mean diameters, linear velocities, or volume flows under 10 and 20% oxygen compared with 0% oxygen. We also determined oxygen levels just under the mesentery with different ambient oxygen levels. These values were the same as in the ambient gas mixture, suggesting that tissue oxygen levels in mesentery are determined by those in the external environment. Oxygen levels in the abdominal cavity averaged 67 mmHg, indicating that mesentery is normally exposed to a high-oxygen environment. We conclude that a change in tissue oxygen tension is not an essential factor in the mechanism of blood flow autoregulation in cat mesentery.

Animals↗
PubMed1987

Rat venule mechanical characteristics during venous pressure elevation.

The purpose of this study was to compare the in vivo mechanical characteristics during venous pressure elevation of two sizes of venules in the intestinal muscularis of anesthetized Wistar rats. The two venules studied were the first-order venule (1V), ID = 71.2 +/- 3.3 microns [12] (means +/- SE [n]) and the small collecting vein (SCV), ID = 134.4 +/- 9.1 microns [12]. Vessel diameters and servonull pressures were measured as venous pressure was elevated with a snare about the vein of the isolated segment. The distension characteristics of the two vessels were significantly different, with the 1V evidencing greater strains (percent change from control diameter) and in vivo distensibilities [D = (delta lumen area/lumen area)/delta pressure] than the SCV at all pressure elevations above control. The 1V and SCV mean wall elastic moduli (calculated using Rhodin's measurements of venule control wall thickness) reflected these differences: the initial 1V wall Young's modulus was low and changed little during the vessel distension, whereas the SCV modulus was greater at control and increased sharply with strain in a nonlinear fashion. Although a portion of these differences can be attributed to different initial hoop wall stress levels, the SCV elastic modulus was significantly greater than the 1V modulus at comparable levels of wall stress. Both active and passive factors may contribute to these in vivo differences in elastic modulus, but this experiment does not distinguish between them.

Animals↗
PubMed1987

Venule distension properties in Wistar, Wistar-Kyoto, and spontaneously hypertensive rats.

The purpose of this study was to determine whether venule distension characteristics are modified in denervated venules in the spontaneously hypertensive rat (SHR) during the developmental stage of hypertension. The distension of denervated first-order venules (1V) and small collecting veins (SCV) in the intestine of 7- to 8-wk-old SHR, Wistar-Kyoto (WKY), and Wistar rats were measured with intravital microscopy during venous pressure elevation. Diameter strain and distensibility were calculated for the 1V and SCV from vessel diameter and servo-null pressure. The Wistar 1V underwent larger strains and distensibilities than the WKY or SHR vessels, which had similar characteristics. For the SCV, the Wistar and WKY strains and distensibilities were similar, with the SHR different from these at only certain pressure elevations. Thus no consistent patterns of altered distension characteristics were found in denervated SHR SCV or 1V compared with its controls. This study does not distinguish between changes in local active and passive factors in the vessel wall which may influence distension. Our results may be consistent with disease mechanisms in the 7- to 8-wk-old SHR which leave these local factors unchanged or with mechanisms which have local venular effects that counterbalance each other, leaving the distension behavior of the denervated venules unchanged.

Animals↗
PubMed1987

Hypospadias and urethral abnormalities in Down syndrome.

In the course of general medical evaluations of 149 children and adolescents (younger than 21 years of age) and 11 adults with Down syndrome, five of the 77 males were noted to have dorsal urethral duplications. In all instances, there proved to be a single urethral meatus. The second opening led into a pit or blind channel, reflecting the presence of a distal hypospadias. In these five patients, laboratory studies were normal, nephrology histories were negative, and radiographic studies did not demonstrate any anatomic abnormalities of the urethra, ureters, or kidneys. These findings indicate that there is an increased occurrence of distal hypospadias in males with Down syndrome that may present with dorsal urethral duplications and/or glanular hypospadias.

Abnormalities, Multiple↗
PubMed1986

Enhanced replication of murine cytomegalovirus in murine leukemic lymphocytes.

Replication in vitro of murine cytomegalovirus was found to be enhanced in lymphoid cells from leukemic (AKR/J) mice as compared with similar cells from nonleukemic animals. Prolonged productive murine cytomegalovirus infection in lymphoid organs in vivo was demonstrable only in leukemic AKR/J mice. Latent nonproductive murine cytomegalovirus infection established in young nonleukemic AKR/J mice was invariably reactivated and expressed in salivary glands and lymphoid organs after these animals became leukemic.

Animals↗
PubMed1984

Relationship of thyroid hormone patterns to survival in canine hemorrhagic shock.

6 of 13 dogs subjected to 1 h of hemorrhagic shock (BP = 45-50 mm Hg) died during the first convalescent day. Nonsurvivors had lower baseline plasma concentrations of total and free T4 and T3, as well as rT3, and higher T3 uptake values. During shock, dogs that died had significantly lower plasma levels of total and free T4 and T3 and higher T3 uptake. In general, intergroup differences were accentuated during resuscitation. After volume replenishment, indices of thyroid function had stabilized or improved in survivors, but were still deteriorating in dogs that ultimately died. There were no consistent hemodynamic differences between the two groups. Thus, parameters of thyroid metabolism appear to be good prognostic indicators in canine hemorrhagic shock.

Animals↗
PubMed1984

Cytomegalovirus infection of the fetus and neonate.

Human CMV infection, the most common virus infection of the fetus and neonate, can occur in utero as "congenital infection" or during the first weeks of life as "perinatal infection." Congenital infection presents either as clinically apparent or as silent infection. Perinatal CMV infection is a common form of CMV acquisition and produces minimal, if any, disease in the full-term infant. The relative occurrence of the viral syndromes in the population and means to prevent this infection are discussed.

Antibodies, Viral↗
PubMed1983

Cytomegalovirus-specific cell-mediated immunity during pregnancy in lower socioeconomic class adolescents.

The role of maternal cytomegalovirus (CMV)-specific cellular immunity in gestational CMV excretion and transmission of congenital infection was assessed by studying CMV-specific mononuclear proliferation (CMV-MP) longitudinally during pregnancy in 59 lower socioeconomic class adolescents. CMV-MP was absent in mothers seropositive for CMV on more than 40% of occasions tested, but no significant difference was noted at any time in frequency or degree of CMP-MP between the 16 mothers who shed virus and the 29 who were seropositive for CMV but did not shed virus. The presence of CMV-MP did not preclude gestational CMV excretion. The lone mother who bore a congenitally infected infant lacked CMV-MP on all three occasions when she shed virus. CMV-MP was noted in cord blood from 14 uninfected infants of seropositive mothers. Maternal CMV-specific cellular immunity is not the major determinant of gestational CMV excretion, but the extent of its role in modulating transmission of congenital infection is yet unclear.

Adolescent↗
PubMed1983

Cytomegalovirus-specific cell-mediated immunity in lower-socioeconomic-class adolescent women with local cytomegalovirus infections.

The factors that regulate cytomegalovirus (CMV) excretion from the genitourinary tract are poorly understood. To assess the role of cell-mediated immunity in such excretion, a CMV-specific mononuclear blastogenesis assay was used to study a predominantly lower-socioeconomic-status population of 92 healthy nonpregnant adolescent women who also had CMV complement-fixing antibody titers and viral cultures of cervix, urine, saliva, and blood performed. Eighteen were studied more than once. No blood cultures were positive and no seroconversions were noted. There was no significant difference for frequency or degree of systemic CMV-specific blastogenesis between the 20 who were culture positive and the 41 who were seropositive but culture negative, although 40% of the culture-positive group and 27% of the seropositive, culture-negative group lacked CMV-specific blastogenesis. One of 31 seronegative subjects displayed CMV-specific blastogenesis. No systematic deficits were noted in any groups or individuals for E rosette number or mitogen response, though some isolated significant differences among groups for mitogen responses existed. Local CMV excretion in the study population was not related to systemic CMV-specific mononuclear blastogenesis.

Adolescent↗