Search PubMed⌕ Search

Biomedical subjects

J Morrison

Publications and source records attributed to J Morrison.

At least 55 records · Page 3Linked to original sources
PubMed1998

Footwall refrigeration along a detachment fault: implications for the thermal evolution of core complexes

Oxygen isotope compositions of epidote and quartz from chloritic breccias that underlie the detachment fault in the metamorphic core complex of the Whipple Mountains yielded quartz-epidote fractionations that range from 4.1 to 6.4 per mil and increase systematically toward the fault. These fractionations give mean temperatures that decrease from approximately 432 degrees C at 50 meters below the fault to approximately 350 degrees C at 12 meters below the fault. This extreme thermal gradient of 82 degrees C over 38 meters (2160 degrees C per kilometer) is best explained by advective heat extraction by means of circulating surface-derived fluids. Models of lithospheric extension consider only conductive cooling resulting from tectonic denudation and thus require revision to include fluid-induced fault-zone refrigeration.

Journal Article↗
PubMed1998

Synergistic effect between IL-10 and bcl-2 genotypes in determining susceptibility to systemic lupus erythematosus.

OBJECTIVE: To determine whether genes participating in programmed cell death, including bcl-2, IL-10, Fas-L, and CTLA-4, may contribute to the genetic predisposition to systemic lupus erythematosus (SLE). METHODS: First, intragenic markers for the bcl-2, IL-10, Fas-L, and CTLA-4 genes were characterized and their extent of polymorphism in normal populations was determined. The allelic distribution of these gene markers in a large Mexican American SLE cohort of 158 patients and 223 ethnically matched controls was determined using fluorescent-labeled primers and semiautomated genotyping. RESULTS: The bcl-2, Fas-L, and IL-10 loci showed significantly different allelic distribution in SLE patients compared with controls, indicating an association between these genes and SLE. No association was found between SLE and the CTLA-4 gene. Further analysis revealed a synergistic effect between susceptibility alleles of the bcl-2 and IL-10 genes in determining disease susceptibility. Alone, the presence of each of these alleles was associated with a moderate increase in SLE risk, while the occurrence of these alleles together increased the odds of developing SLE by more than 40-fold. CONCLUSION: The results suggest that individuals carrying specific genotypes of both bcl-2 and IL-10 are at significant risk of developing SLE.

Abatacept↗
PubMed1998

Alterations in renal microcirculation during cardiopulmonary bypass.

BACKGROUND: This study was designed to investigate renal microvascular changes during cardiopulmonary bypass. METHODS: Kidneys were harvested from each of four groups of 6 pigs. Group A were anesthetized and heparinized only. The remaining three groups underwent cardiopulmonary bypass at 28 degrees C, group B for 30 minutes and groups C and D for 120 minutes; group D had an additional 30 minutes of normothermic perfusion at the end of the experiment. Renal cortical blood flow was measured using radiolabeled microspheres. Microvascular morphology was defined by corrosion casting and scanning electron microscopy. RESULTS: In group A, renal vascular resistance was 61+/-5.1 mm Hg x mL(-1) x min(-1). This value decreased to 28+/-7.8 in group B and 25+/-4.0 in group C (p < 0.05), and increased in group D to 40+/-4.1 (p < 0.05 versus groups A, B, and C). Cortical thickness, as measured by microvascular casts in groups A, B, and C, was 33, 34, and 31 mm, respectively, with equal distribution of the resin to the superficial and deep cortex but was significantly reduced in group D to 22 mm (p < 0.05 versus groups A, B, and C), with failure of the resin to fill the superficial cortical layer. Diameters of glomeruli as seen on the casts were 111+/-10.38 microm in group A, 100+/-9.24 microm in group B, and 82+/-4.4 microm in group C (p < 0.05 group A versus group C). The glomeruli from group D were still significantly smaller than group A (93+/-10.35 microm, p < 0.05). Mean glomerular capillary diameters were 4.65+/-0.26 microm in group A, 3.9+/-0.16 microm in group B, 3.6+/-0.19 microm in group C, and 3.65+/-0.3 microm in group D (p < 0.05 group A versus groups B, C, and D). CONCLUSIONS: Hypothermic nonpulsatile cardiopulmonary bypass decreased renal vascular resistance, but the superficial and deep layers of the cortex were perfused equally. Glomeruli were reduced in size because of capillary narrowing. This was consistent with diversion of blood through bypass channels. With restoration of normothermia, underperfusion of the superficial cortex occurred, with potential for damage to these nephrons during the increased metabolic demands of rewarming.

Anesthesia, Inhalation↗
PubMed1998

Prolonged myocardial hibernation exacerbates cardiomyocyte degeneration and impairs recovery of function after revascularization.

OBJECTIVES: We sought to define the effects of time on contractile function, morphology and functional recovery after coronary revascularization in patients with dysfunctional but viable (hibernating) myocardium. BACKGROUND: Functional recovery after coronary artery bypass graft surgery in patients with chronic myocardial hibernation is incomplete or delayed. The proposed cause is a progressive temporal degeneration of cardiomyocytes. METHODS: In 32 patients with multivessel coronary disease, regional wall motion analysis was performed in hypoperfused but metabolically active areas before and 6 months after bypass surgery. During bypass surgery, transmural biopsy samples were obtained from the center of the hypokinetic zone for light and electron microscopic analyses. The proposed duration of myocardial hibernation was retrospectively assessed. RESULTS: Patients with a subacute hibernating condition (<50 days) demonstrated a higher preoperative ejection fraction (EF, 50+/-8%), and a better preserved wall motion (WM) in the supraapical wall (-1.4+/-0.4) than did patients with intermediate-term (>50 days, EF 37+/-9%, p < 0.05; WM -2.4+/-1.5, p = 0.08) or chronic (>6 months, EF 40+/-14%, WM -2.7+/-0.9, p < 0.005) ischemia. Structural degeneration correlated with the duration of ischemia (r = 0.56, p < 0.05). Postoperative recovery of function was enhanced in patients with a short history of hibernation compared with patients with an intermediate-term or chronic condition (EF 60+/-10% vs. 40+/-10%, p < 0.001, and vs. 47+/-14%, p < 0.05). CONCLUSIONS: Hibernating myocardium exhibits time-dependent deterioration due to progressive structural degeneration with enhanced fibrosis. Early revascularization should be attempted to salvage the jeopardized tissue and improve postoperative outcome.

Aged↗
PubMed1998

Clinical issues surrounding the use of terbutaline sulfate for preterm labor.

beta-mimetics have been prescribed by physicians to arrest or prevent premature labor for more than 20 years. Although not approved by the Food and Drug Administration (FDA) for tocolytic use, terbutaline sulfate has been the most widely prescribed beta-mimetic in the United States. Recently, the role of terbutaline in the treatment and prevention of preterm labor has been questioned by the FDA. Because the off-label use of drugs is a formally accepted practice in medicine when scientific studies support such use, we reviewed the currently available clinical literature on terbutaline use in various routes of delivery: intravenous, oral, and subcutaneous via infusion pump. This review describes the clinical evidence that supports the safe and effective use of terbutaline as a tocolytic agent in certain patient populations. Practicing physicians should continue to have unrestricted use of terbutaline for tocolysis as one of the few remaining therapeutic options remaining in the fight against preterm birth.

Administration, Oral↗
PubMed1998

A staffing model based on workload in three VA mental health clinics.

In the era of managed care, agencies that provide mental health care can cope with the increasing volume of patients and the increasing severity of their conditions by having a variety of mental health professionals provide services. A model for determining workforce needs for outpatient mental health clinics is described. The model was used with workload data from three Veterans Affairs clinics to determine that two psychiatrists and five or six nonpsychiatrists should be able to evaluate 400 new patients a year and provide ongoing care for 2,300 patients a year in such settings. The method can be adapted to determine workforce needs for other outpatient clinical settings.

California↗
PubMed1998

Clinical and microbiological evaluation of a bioabsorbable and a nonresorbable barrier membrane in the treatment of periodontal intraosseous lesions.

Clinical and microbiological features of periodontal healing in barrier membrane-treated sites were determined in a randomized clinical trial. The study included 10 patients with advanced adult periodontitis and a minimum of one set of similar 2 to 3 wall intraosseous periodontal lesions with no furcation involvement. In each patient, one periodontal lesion was treated with a biodegradable membrane and a contralateral lesion with a nonresorbable barrier membrane. Within the preceding 3 months of regenerative therapy, all patients received full mouth osseous surgery except for the sites for regeneration, were instructed in oral hygiene, and were prescribed systemic ciprofloxacin and metronidazole (250 mg of each, TID, 8 days), starting 7 days before membrane placement. At baseline and at 6 months postsurgery, probing depth and clinical attachment level were assessed in each study site. The subgingival presence of suspected periodontal pathogens was determined by non-selective and selective culture and by DNA probe analyses, and of human cytomegalovirus (HCMV) and Epstein-Barr virus type 1 (EBV-1) by a nested-polymerase chain reaction detection method. At baseline, the barrier-treated sites did not differ significantly in clinical and microbial parameters. Mean baseline probing depth was 7.8+/-1.1 mm for bioabsorbable and 7.9+/-1.3 mm for nonresorbable barrier-treated sites. At 6 months, sites treated with bioabsorbable barrier revealed 4.6+/-1.7 mm gain of clinical attachment (range: 1 to 7 mm) and sites treated with nonresorbable barrier 4.2+/-2.0 mm (range: 1 to 8 mm). The 11 barrier-treated sites that harbored 10% or less bacterial pathogens and were free of HCMV and EBV-1 averaged significantly more clinical attachment gain than the 9 sites that yielded more than 10% bacterial pathogens and/or test viruses (5.6 mm versus 3.0 mm; P=0.005). The present data suggest bioabsorbable and nonresorbable barriers provide similar clinical healing of 2 to 3 wall intraosseous periodontal lesions, emphasize the importance of controlling bacterial pathogens prior to and during periodontal healing, and point to the possible detrimental role of HCMV and EBV-1 in periodontal repair.

Adult↗
PubMed1997

The effects of cardioplegic arrest and reperfusion on the microvasculature of the heart.

OBJECTIVES: Despite laboratory evidence of leucocyte involvement in reperfusion injury, cardiac surgical clinical trials do not support the therapeutic effectiveness of leucocyte filtration. Furthermore, the direct effects of crystalloid cardioplegia and reperfusion on the capillaries of the heart have yet to be elucidated. We tested the effects of cardioplegic arrest and reperfusion both with and without leucocyte depletion, in a model of cardiopulmonary bypass that mimics clinical cardiac surgical conditions. METHODS: Four groups of Landrace pigs were studied. Group A (n = 6) underwent 30 min of hypothermic (28 degrees C) cardiopulmonary bypass. Groups B (n = 6), C (n = 6) and D (n = 6) also had 90 min of cardioplegic arrest. Group C was then reperfused with whole blood, while Group D was reperfused with leucocyte-depleted blood. Microvascular methylmethacrylate corrosion casts were made at the end of the experimental period. Myocardial vascular anatomy was defined by electron microscopy and capillary abundance derived from this and from the weight of casts from representative areas. Leucocyte deposition was assessed using radioisotope-labelled leucocytes. Ischaemic damage to tissues was graded according to light and electron microscopic findings. RESULTS: In Group A the mean (+/- S.D.) vascular cast weight/volume of myocardium (density) was 125 +/- 9 mg/mm3. After cardioplegic arrest (Group B), it fell to 74 +/- 7 mg/mm3 (P < 0.0001) due to absence of capillaries, although arterioles, venules and non-nutritive bypass vessels remained patent. Following reperfusion with whole blood (Group C), capillary numbers partially recovered but luminal diameters were reduced with a cast density of 94 +/- 5 mg/mm3 (P < 0.0001 versus Group A and B). Leucocyte-depleted (87-92%) reperfusion in Group D did not affect cast density (90 +/- 3 mg/mm3; P = 0.17). Coronary vascular resistances in Groups C and D rose slightly, but not significantly, during reperfusion. CONCLUSIONS: Following cardioplegic arrest, microvascular changes are marked. These changes are partially reversed by 30 min reperfusion. Leucocyte depletion does not ameliorate these effects in this model.

Animals↗
PubMed1997

Vertical transmission of human immunodeficiency virus.

We discuss the interactions between mother and infant that influence the transmission of HIV. Potential routes of infection are identified, and maternal and infant risk factors for transmission are explored. The role of the immune system in controlling HIV infection in the infant is discussed. Finally, preventive measures for reducing vertical transmission are proposed and evaluated.

Anti-HIV Agents↗
PubMed1996

Dystrophic neurite formation associated with age-related beta amyloid deposition in the neocortex: clues to the genesis of neurofibrillary pathology.

The formation of dystrophic neurites associated with beta amyloid plaques in Alzheimer's disease (AD) appears to involve a transformation of normal neuronal cytoskeletal proteins. In order to investigate what may be the earliest neuronal changes associated with the development of dystrophic neurites, we have examined the neurochemical profile of abnormal neuritic processes associated with the beta amyloid deposition in non-AD, aged cases. In all non-AD individuals demonstrating some degree of beta amyloid deposition in the superior frontal gyrus, clustered swollen and ring-like structures, located principally in layers II and III, were labeled with antibodies to phosphorylated and nonphosphorylated domains of the middle and high molecular weight neurofilament subunits. These abnormal neurites were not immunolabeled for tau or ubiquitin or stained with thioflavine S. Double labeling for neurofilaments and thioflavine S confirmed that these clusters of dystrophic neurites were associated with plaque-like deposits. These results show that anatomically and neurochemically specific forms of dystrophic neurites can occur in non-AD cases that contain beta amyloid deposition. If these abnormal neurites correspond to an immature form of the dystrophic neurites found in the neuritic plaques of Alzheimer's disease, then neurofibrillary pathology associated with this disease may begin with an initial misprocessing and accumulation of neurofilament proteins. Furthermore, these data are consistent with the proposal that the development of neurofibrillary pathology may begin with neurofilamentous hypertrophy in damaged distal processes followed by reactive changes in the cell bodies of origin of these fibers involving cytoskeletal alterations that ultimately lead to neurofibrillary tangle formation.

Aged↗
PubMed1996

Yeast artificial chromosome cloning and chromosomal localization of the abundant odontogenic keratocyst protein elafin.

An imbalance in human leucocyte elastase (HLE) activity is widely recognized to play an important pathological role in a number of human diseases. An earlier report has described greater transcription of elafin, an endogenous inhibitor of HLE, in epithelia of odontogenic keratocysts of the jaw than in normal oral mucosa. The elafin gene was now localized to chromosome 20q11.2-13.1 using a combination of somatic cell-hybrid panel screening and fluorescence in situ hybridization using a biotinylated DNA probe prepared from isolated yeast artificial chromosomes. No other positive fluorescent signals were observed. This eliminates the elafin gene as a candidate gene for naevoid basal-cell carcinoma syndrome, as the gene for this syndrome localizes to chromosome 9q23.1-31. The elafin yeast artificial chromosome DNA is to be subcloned to identify polymorphic microsatellite markers that will establish whether this gene is frequently amplified in oral neoplastic tissue.

Basal Cell Nevus Syndrome↗
PubMed1996

The benefits of active rewarming after cardiac operations: a randomized prospective trial.

We conducted a prospective, randomized trial of three methods of rewarming patients after hypothermic cardiopulmonary bypass. Patients underwent either coronary artery bypass grafting or first-time valve replacement and were cooled to 32 degrees C during bypass. No significant differences existed among the groups as regards operative or preoperative parameters including hemodynamics and blood use. The patients actively warmed with a convective (Bair Hugger system, 3 hours) or a conductive blanket (electric overblanket, 4 hours) reached normothermia more quickly than those warmed with the space blanket (7 hours). This was reflected in significantly earlier extubation in the former two groups: Bair Hugger system 10.8 +/- 0.6 hours, electric blanket 11.3 +/- 1.0 hours, and space blanket 14.8 +/- 0.8 hours. Patients warmed with the space blanket required a higher dosage of morphine over the first 12 hours than those warmed with the electric blanket (10.4 vs 6.5 mg; p = 0.004), which may account for some of the differences between these two groups. No differences could be demonstrated between the two active blankets. On economic grounds we therefore recommend the reusable electric blanket for routine use.

Aged↗
PubMed1996

Comparison between broad-band ultrasound attenuation of the calcaneum and total body bone mineral density in children.

We measured broad-band ultrasound attenuation (BUA) in the calcaneum using the prototype Paediatric Contact Ultrasound Bone Analyser (CUBA) and total body bone mineral density (TBBMD) using dual-energy X-ray absorptiometry (DXA) (Hologic QDR-1000W) in 58, 7-17-year-old healthy children and adolescents. Calcaneal BUA was significantly related to TBBMD (r = 0.74, p < 0.001), and both the calcaneal BUA and TBBMD were significantly correlated with age and body weight. We conclude that calcaneal BUA reflects bone mineral density (BMD) in healthy children and adolescents; however, BMD measured by CUBA appears to be less sensitive than that measured by DXA. Since BUA reflects structural properties of bone, as well as density, it may complement radiological techniques of bone density measurement in the assessment of paediatric conditions associated with fracture risk.

Absorptiometry, Photon↗