Biomedical subjects
Publications and source records attributed to D Bennett.
We report a bone marrow transplant patient who developed a reversible episode of cortical blindness, a rare complication of cyclosporine therapy. We review previously reported cases and the mechanisms involved in this complication.
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The t complex of the mouse has an important role in male germ cell development and function. Multiple mutations in the t complex interact to alter profoundly the transmission ratio of t complex-bearing sperm or to cause complete sterility or semisterility. We have isolated a multigene family, tctex-1, by screening a testicular cell cDNA library with two reciprocally subtracted testicular cDNA probes. The tctex-1 gene family produces an abundant, virtually germ cell-specific transcript that is 8-fold overexpressed in t homozygotes. The aberrant expression of tctex-1 is solely dependent on the t haplotype genes and occurs only in germ cells. The chromosomal location and pattern of expression of tctex-1 make it a candidate for involvement in male sterility.
OBJECTIVE: To assess oesophageal Doppler ultrasonography as a convenient means of optimising positive end expiratory pressure for maximal delivery of oxygen to tissues. DESIGN: Measurements of blood flow, arterial oxygen saturation, and cardiac output by thermodilution (when available) at baseline and at 20-30 minutes after each incremental increase (2.5-5.0 cm H2O) in positive and expiratory pressure to a maximum of 20.0 cm H2O. If the cardiac output fell by more than 15% measurements were repeated after stepwise decreases in positive end expiratory pressure. No other manoeuvre such as endotracheal suction or changing ventilator settings, drug or fluid dosage, or the patient's position was performed for at least one hour before the start of the study or during it. SETTING: Intensive care unit. PARTICIPANTS: 10 Patients being mechanically ventilated for acute respiratory failure who had stable haemodynamic and blood gas values and required a fractional inspired oxygen concentration of greater than or equal to 0.45. They were assessed on a total of 11 occasions. INTERVENTIONS: Incremental increases in positive end expiratory pressure followed when indicated by stepwise decreases. END POINT: The positive end expiratory pressure providing maximal delivery of oxygen to tissues. MEASUREMENTS AND MAIN RESULTS: Arterial oxygen saturation increased with positive end expiratory pressure in all patients by an average of 6.1%. In nine of the 11 studies, however, cardiac output fell by 15% to 30% after the second increment. On the two other occasions cardiac output and oxygen delivery rose by up to 54%. Positive end expiratory pressure was decreased on seven occasions; there was considerable individual variation in the time taken for cardiac output to rise and arterial oxygen saturation to fall. In six patients good agreement was seen between the results from Doppler ultrasonography and thermodilution, the mean of the differences being -0.3% with narrow limits of agreement (-14.4% to 13.9%). CONCLUSIONS: Oesophageal Doppler ultrasonography is a rapid, safe, and reliable technique for optimising positive end expiratory pressure to obtain maximal delivery of oxygen to tissues. The results show the need to consider haemodynamic consequences when altering positive end expiratory pressure.
Twelve specific pathogen free cats were used to investigate the role of calicivirus in causing lameness. These were divided into two groups each of six cats; one group of cats had previously been vaccinated, the other had not. Three cats in each group were given live vaccine virus (F9 related) by the subcutaneous route and two in each group were challenged intranasally with field virus (A4), either four or seven days before euthanasia. The other two cats were controls. Virus was isolated from the oropharynx of five cats and the conjunctiva of a single cat. Four of these cats had been given the field virus and two the vaccine strain; the latter two cats had been previously immunised and had high circulating neutralising antibodies to calicivirus. No virus was isolated from the joints of any cat but immunofluorescence examination revealed viral antigens within the synovial macrophages of 14 joints from five cats, three having been given the field virus and two the vaccine virus seven days before euthanasia. Immunofluorescence also demonstrated the presence of immunoglobulin and complement within synovial macrophages suggesting that the virus was in the form of an immune complex. No lameness was reported in any cat and the synovial histological changes were minimal.(ABSTRACT TRUNCATED AT 250 WORDS)
T and Tc are dominant mutations in the mouse that affect neuroaxial development when heterozygous and cause embryonic death when homozygous. Embryos were analyzed individually by two-dimensional gel electrophoresis at 9 1/2 days gestation, 1 day before homozygotes die in utero. A comparison of the protein patterns of mutant homozygotes with those of their littermates revealed a set of proteins (T-proteins) that showed isoelectric point (pl) polymorphism. All the T-proteins were more basic in mutant homozygotes. These polymorphisms could be detected, although they were less pronounced, in embryos as young as 7 1/2-day presomite stages, when it is impossible to distinguish homozygous mutants grossly. Interestingly, the same proteins show a pl shift from basic to acidic in wild-type embryos during development from 7 1/2 to 9 1/2 days. Thus, it appears that in T and Tc mutants a developmentally specific posttranslational acidic modification of these proteins is disturbed. The likely cause of the abnormality is a defect in some mechanism for phosphorylation, since the T-proteins of wild-type embryos were shifted to higher pls by phosphatase treatment. This disturbance appears to be localized to axial structures (neural tube, somites, and surrounding mesenchyme) since only these structures, and not the rest of the mutant homozygous embryos, contain abnormally basic T-proteins.
Curtailed (Tc), a dominant mutation on mouse chromosome 17, causes a tailless phenotype and occasional hindlimb paralysis in heterozygotes. Histologically, Tc/+ embryos show a variety of abnormalities including budding and ventral duplication of the developing spinal cord, duplication and intermittent absence of the notochord, and partial or complete absence of bony vertebrae, all posterior to midliver level. When Tc is heterozygous with t-haplotypes that contain the "tail interaction factor," tct, the phenotype is more severe, and a dorsal blood blister exists in the lumbosacral area. Our microscopic observations reveal that Tc/tw5 mice have a lumbosacral spina bifida with meningomyelocele. This results from the absence of bony vertebrae, extensive thinning of the dermis dorsally, and the rupturing of the previously closed neural tube, probably by increased cerebrospinal fluid (CSF) pressure on the necrotic, attenuated roof plate. Thinning of the roof plate, which facilitates the rupturing of the spinal cord, is not observed in Tc/+, which suggests that this phenomenon is associated with the interaction of Tc with the t-allele. Later in the development of Tc/tw5 embryos, adjacent blood vessels are ruptured, resulting in hemorrhage into the CSF space to give the external appearance of a blood blister. Tc/+ mice also show an absence of bony vertebrae dorsally in the lumbosacral region, but they lack the dorsal blood blister, and the dermal layer overlying the bony defect retains its normal thickness; these observations describe a spina bifida occulta.
Autoimmunity to collagen was investigated in several naturally occurring arthropathies of the dog. Increased levels of serum anti-native collagen type II antibody, as assessed by ELISA, were shown in 72.4% of dogs with rheumatoid arthritis (RA), 88% of dogs with infective arthritis (IA) and 52% of dogs with osteoarthritis (OA) (p less than 0.001). The mean levels of antibody in cruciate disease patients (CR) were also significantly increased compared to control dogs (p less than 0.01). Serum anti-collagen antibody in OA dogs correlated with that in precipitated serum immune complexes. There was also a correlation between anti-collagen antibody level in synovial fluid and in synovial fluid complexes in dogs with rupture of the cranial cruciate ligament. In all patient groups, collagenase digestion of polyethylene glycol (PEG) precipitates from sera and synovial fluids caused a significant rise in specific antibody levels to collagen, indicating the presence of collagen-anti-collagen complexes in all arthropathies. In dogs with RA, the levels of collagen-specific antibody in synovial fluid complexes correlated with the total IgG in these complexes. These findings implicate collagen-anti-collagen complexes in the pathogenesis of naturally occurring joint diseases in the dog, but they are unlikely to be the primary aetiological mechanism.
Invasive hemodynamic monitoring has recognized pitfalls and complications. Some of these may be detected and avoided by the adjuvant use of Doppler ultrasound measurement of aortic blood flow.
Previous studies have shown that haemorrhage in Lassa fever is associated with abnormal in vitro platelet aggregation and a high mortality. In Sierra Leone we studied platelet aggregation in healthy local subjects, patients with laboratory-confirmed Lassa fever and febrile patients in whom Lassa virus infection was excluded. There were no significant differences in the mean platelet counts of these groups. Patients with fulminant Lassa virus infection showed a gross depression of in-vitro platelet responsiveness to 1 and 5 microM ADP and 4 micrograms/ml collagen compared to other groups (P = 0.0004-0.0008 when compared to healthy controls, P = 0.002-0.0008 when compared to mild Lassa fever patients). When plasma samples from five of these patients were mixed 1:1 with control platelet-rich plasma, a marked inhibition of ADP-induced aggregation was observed. No inhibitory activity was detected in plasma obtained from healthy subjects or febrile control patients. The presence of inhibitor was strongly associated with the occurrence of haemorrhage (P = 0.03), depression of platelet aggregation (P = 0.004) and severity of Lassa fever (P = 0.007).
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1. Procedures that increase atrial pressure, such as head-down tilt, result in an increase in plasma atrial natriuretic peptide (ANP) and a natriuresis, but a direct cause-and-effect relationship between these two responses has not been established. This study was undertaken to compare the effects of head-down tilt with exogenous ANP on renal function. 2. Eight normal sodium-replete volunteers underwent a 3 h placebo infusion, a 3 h ANP infusion at 1.2 pmol kg-1 min-1 and a 3 h period of head-down tilt. Each procedure was performed on a separate day, in random order. 3. ANP and head-down tilt produced similar increases in sodium excretion (65 +/- 24 and 68 +/- 16%, respectively). ANP did not increase urine flow significantly more than placebo. Head-down tilt increased urine flow significantly more than placebo and ANP. 4. Plasma ANP rose from 8.1 +/- 1.0 to 11.4 +/- 2.5 pg ml-1 during head-down tilt and from 6.5 +/- 1.4 to 32.3 +/- 10.7 pg ml-1 with ANP infusion. 5. ANP infusion had no significant effects on systemic haemodynamics whilst head-down tilt increased cardiac output and reduced heart rate and an index of systemic vascular resistance. 6. ANP infusion, whilst achieving a natriuretic response similar to that of tilt, was associated with a 3-fold higher mean plasma ANP level. Although plasma ANP rose during both ANP infusion and tilt, there was a lack of correlation between natriuretic response and plasma ANP. 7. The results are not compatible with a direct cause-and-effect relationship between plasma ANP and sodium excretion during head-down tilt.
Thirty two domestic dogs with naturally occurring polyarthritis were investigated to determine the contribution of autoimmunity in the pathological mechanisms. Comparisons were made with canine infective arthritis (12 dogs), osteoarthritis (32), and osteoarthritis secondary to rupture of the cranial cruciate ligament (19). Rheumatoid factors, immune complexes, and complement fixation (C1q binding) were measured in sera and synovial fluids. Compared with normal dogs (32), dogs with rheumatoid arthritis (RA) had increased serum and synovial fluid immune complexes and rheumatoid factors. Increases were generally also seen in dogs with other arthropathies, however. Rheumatoid factors were higher in sera than in synovial fluids. Rheumatoid factors correlated with immune complex levels and complexed rheumatoid factor only in the group of dogs with RA. Both rheumatoid factors and immune complexes may contribute to the pathogenesis of canine RA but are considered to arise as a result of non-specific inflammatory mechanisms in the non-rheumatoid groups.
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Electrocardiograms from 32 patients with acute Lassa fever were abnormal in over 70% of cases. The changes noted included non-specific ST-segment and T-wave abnormalities, ST-segment elevation, generalized low-voltage complexes, and changes reflecting electrolyte disturbance. None of the abnormalities correlated with clinical severity of infection, serum transaminase levels, or eventual outcome. ECG changes are common in Lassa fever, but usually unassociated with clinical manifestations of myocarditis.
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The relative value of exercise testing, late potentials and simple clinical assessment in predicting ischemic and arrhythmic events during follow-up after acute myocardial infarction (AMI) was investigated prospectively in a population of 176 consecutive patients surviving to 7 days after AMI. During 15 +/- 9 (range 3 to 24) months of follow-up, there were 23 ischemic events (2 fatal reinfarctions, 6 nonfatal reinfarctions and 16 patients who underwent coronary artery bypass grafting, 1 after reinfarction) and 11 arrhythmic events (7 symptomatic ventricular tachycardias and 4 sudden cardiac deaths). Stepwise multiple regression analysis showed that out of 11 variables, including exercise testing, late potentials and clinical data, exercise testing was the only independent variable predicting the occurrence of ischemic events (p less than 0.05 not including coronary artery bypass grafting and p less than 0.002 including it). Arrhythmic events were predicted, in order of importance, by Killip class (p less than 0.05), late potentials (p less than 0.005), previous AMI (p less than 0.009), occurrence of in-hospital complications (p less than 0.005) and non-Q-wave AMI (p less than 0.02). The presence of late potentials provided independent prognostic information from the Killip class and the result of exercise testing in predicting both arrhythmic and ischemic events. Exercise testing, late potentials and clinical assessment provide complementary prognostic information in postinfarction patients.
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