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Biomedical subjects

C J Baker

Publications and source records attributed to C J Baker.

At least 91 records · Page 5Linked to original sources
PubMed1995

Short-term perioperative anticonvulsant prophylaxis for the surgical treatment of low-risk patients with intracranial aneurysms.

The long-term use of anticonvulsant medication to prevent postoperative seizures in patients with aneurysms has been accepted medical practice for many years. The low incidence of seizures in more recent aneurysm series makes it appropriate to re-evaluate the use of prophylactic anticonvulsants to prevent postoperative epilepsy, especially in patients at low risk of seizure disorders. On the basis of preoperative presentation, we categorized 387 of the 420 craniotomies for aneurysms over a 4-year period to be at low risk of seizure. Postoperative anticonvulsant medication in this group was restricted to an average of 3 days. A retrospective analysis of the incidence of early postoperative seizures and late postoperative seizure disorders was performed in the populations of patients with ruptured aneurysms and with unruptured aneurysms with an average follow-up of 2.4 years. The overall seizure rate in the study group was 5.4%. Patients with ruptured aneurysms had an early postoperative seizure rate of 1.5% and a long-term seizure disorder rate of 3.0%. Early and long-term seizure rates for unruptured aneurysms were 2.6 and 4.4%, respectively. No patients who had early seizures went on to develop epilepsy, and all seizure disorders were well controlled once anticonvulsants were begun. These data support the idea that anticonvulsant medication may be safely restricted to the immediate perioperative period for most patients with aneurysms.

Adult↗
PubMed1995

Invasive fungal dermatitis in the < or = 1000-gram neonate.

OBJECTIVE: In 1991, we noted the emergence amongst our extremely low birth weight neonates of a new clinical entity, invasive fungal dermatitis, characterized by erosive, crusting lesions and a high rate of subsequent systemic fungal infection. We sought to define this condition and examine potential risk factors. METHODS: Sixteen neonates with invasive fungal dermatitis were seen during a 2-year period in three Baylor College of Medicine affiliated intensive care nurseries. Seven were confirmed cases, with skin biopsy evidence of invasion beyond the stratum corneum. Nine had a consistent clinical course and a positive potassium hydroxide examination of skin scrapings or isolation of fungi from skin or systemic cultures. Three controls were matched to each case by hospital, date of admission, and birth weight. Data was collected by retrospective chart review. RESULTS: Invasive fungal dermatitis occurred in 5.9% of at-risk infants. Case patients had a mean birth weight of 635 g and developed skin lesions at a mean age of 9 days (range, 6 to 14). Candida albicans was the most commonly implicated pathogen, but other Candida species, Aspergillus, Trichosporon beigelii, and Curvularia were also seen. Disseminated infection occurred in 69%, all due to Candida sp. Case patients were significantly more premature than controls (mean gestation, 24.4 vs 25.9 weeks) and were more likely to be delivered vaginally (81% vs 50%). Postnatal steroids were administered to cases (81%) more often than controls (46%). Case patients had more prolonged hyperglycemia (as assessed by insulin administration) than controls (mean 4.3 vs 2.0 days). CONCLUSIONS: Invasive fungal dermatitis is a disease of the smallest, most immature neonates and is associated with vaginal birth, steroid administration, and hyperglycemia. We speculate that the skin serves as a portal of entry for colonizing fungal species and may thus lead to disseminated infection. Methods to improve skin barrier function may be useful in preventing this disorder.

Candidiasis↗
PubMed1994

Endotracheal colonization with Candida enhances risk of systemic candidiasis in very low birth weight neonates.

OBJECTIVE: To determine whether growth of Candida from an endotracheal aspirate identifies a population of very low birth weight (VLBW; < or = 1500 gm) neonates at increased risk of systemic candidiasis. DESIGN: Prospective evaluation with weekly cultures of endotracheal and rectal specimens to determine colonization status. SUBJECTS: One hundred sixteen VLBW neonates (mean birth weight, 975 +/- 23 gm, estimated gestational age, 27.6 +/- 0.2 weeks) with endotracheal tubes in place who were admitted to a level III nursery between Jan. 8 and Dec. 2, 1992. RESULTS: Of the 116 subjects, 39 infants were colonized with Candida (34%). Thirteen neonates had growth of Candida in one or more cultures of endotracheal specimens. Eleven of these could be examined, and in five systemic disease developed (disease in 5/11 vs 2/26; relative risk = 5.9; 95% confidence interval, 1.34 to 26). Eight infants were colonized with Candida in the first week of life. Seven of these could be examined, and in five systemic candidiasis developed (disease in 5/7 vs 2/30; RR = 9.3; 95% confidence interval, 2.3 to 38.0). CONCLUSIONS: Colonization with Candida occurs frequently in VLBW infants. Progression from colonization to systemic infection is more common in the smallest neonates. Detection of colonization in the first week of life or the growth of Candida from an endotracheal aspirate identifies a group of VLBW neonates with an endotracheal tube in place whose risk of systemic candidiasis is increased. A prospective trial of intervention in this high-risk population is warranted.

Analysis of Variance↗
PubMed1994

Recurrent group B streptococcal infections in infants: clinical and microbiologic aspects.

OBJECTIVE: To describe the potential for recurrence of group B streptococcal (GBS) infection in infants, using pulsed-field gel electrophoresis as an epidemiologic tool. DESIGN: Retrospective review of cases identified by laboratory records and review of the literature. SETTING: Neonatal nurseries of a county hospital system. METHODS: Retrospective review of infants with second episodes of GBS bacteremia or meningitis. Digestion of chromosomal DNA with the restriction enzyme Sma I and separation of fragments by use of contour-clamped homogeneous electric field. RESULTS: Nine cases of recurrent GBS infection were identified during a 14-year period. Eight of the nine infants were born at 25 to 36 weeks of gestation, and one was born at term. The first episode of invasive GBS infection occurred at a mean age of 10.4 days (median, 3 days; range, 1 to 27 days). Parenteral antibiotic therapy was administered for a mean of 13.9 days (median, 14 days; range, 10 to 21 days). Recurrence occurred at a mean age of 42.3 days (median, 48 days; range, 23 to 68 days). One patient died during the second episode; eight infants survived to discharge home. Of seven sets of isolates analyzed from first and second GBS episodes, five were confirmed to be the same genotypically. CONCLUSION: Recurrence of GBS disease in infants may be associated with the original infecting strain or a second acquired strain.

Anti-Bacterial Agents↗
PubMed1994

Analysis of the cucumber malate synthase gene promoter by transient expression and gel retardation assays.

Recently it has been demonstrated that the single-copy malate synthase (MS) and isocitrate lyase (ICL) genes from cucumber are regulated by nutritional status in cucumber cell cultures. In this paper a new cucumber mesophyll protoplast transient expression system is described in which electroporated MS promoter-GUS reporter gene constructs exhibit the same pattern of expression as the endogenous MS gene. Both the electroporated MS-GUS constructs and the endogenous gene are expressed when protoplasts are cultured for 48 h on a non-metabolizable carbon source such as mannitol or 3-methylglucose, and repressed when cultured on a utilizable carbon source such as sucrose, glucose or fructose. A series of deletion mutants identified a region from position -248 to -125 relative to the start of transcription that is essential for expression of the MS-GUS construct under the different metabolic conditions. A 191 bp fragment spanning this region was fused, in both orientations, to the CaMV 35S core promoter. A pattern of metabolic regulation similar to that of the intact MS promoter was observed for these promoter fusion constructs which strongly suggests the presence of enhancer element(s) within this region. Comparison of the 191 bp region with other MS and ICL promoter sequences revealed a region of homology, designated RT. A gel retardation assay was used to assess binding of the 191 bp fragment to whole cell protein extracts from cell cultures expressing MS. Both the unlabelled 191 bp fragment and a synthetic oligonucleotide of RT compete specifically for the demonstrated binding activity.

Base Sequence↗
PubMed1994

Complement and antibody in neutrophil-mediated killing of type V group B streptococcus.

Serious infections caused by type V group B streptococci (GBS) are increasing. The requirements for antibody, complement, and neutrophil receptors in the killing of 12 clinical type V GBS isolates were investigated. When tested at concentrations of 33%, 5% and 1%, a human serum pool promoted neutrophil-mediated killing of the 12 isolates at a mean of 83% +/- 9%, 77% +/- 17%, and 14% +/- 28%, respectively. Addition of heated immune rabbit serum to the 5% or 1% pool increased killing significantly (97% +/- 2% or 80% +/- 15%, respectively, P < .01). With hypogammaglobulinemic serum, complement-mediated killing ranged from 74% +/- 2% for a strain designated resistant to 98% +/- 1% for a strain designated sensitive. Neutrophil-mediated killing was not altered by use of human sera deficient in C4 or C7 but was reduced significantly with C3-deficient serum (P < .05). Maximal inhibition of neutrophil-mediated killing was observed by monoclonal antibody blockade of complement receptor (CR) 3 alone or in combination with CR1 or Fc receptor III. Thus, C3 is required and specific antibody promotes neutrophil-mediated killing of type V GBS. Neutrophil CR3 and either CR1 or Fc receptor III optimize phagocytosis. A number of host responses function in concert to effect optimal neutrophil-mediated killing of clinical isolates of type V GBS.

Animals↗
PubMed1994

Carriage of group B Streptococci in pregnant Gambian mothers and their infants.

The prevalence of group B streptococcal (GBS) colonization was studied in 136 pregnant women and their newborn infants by collecting vaginal and rectal swabs from the mothers and throat, rectal, and umbilical swabs from their infants. Maternal and infant colonization rates were 22% and 23%, respectively. One-third of infants born to colonized mothers and 15% of infants born to noncolonized mothers had GBS isolated. Of GBS-colonized infants, 50% remained colonized at the mean age of 2 months. Type V was the commonest serotype among GBS isolates from mothers and infants; type III strains were uncommon. The rarity of GBS disease in Gambian infants may be due to low rates of maternal carriage with the more virulent GBS serotypes.

Adult↗
PubMed1994

Deliberate mild intraoperative hypothermia for craniotomy.

BACKGROUND: Despite enthusiasm for the use of mild hypothermia during neurosurgical procedures, this therapy has not been evaluated systematically. This study examined the feasibility and safety of deliberate mild hypothermia and rewarming. METHODS: Thirty patients scheduled for craniotomy were assigned to either a normothermic or mildly hypothermic group. Tympanic membrane temperature was monitored at anesthetic induction, throughout the isoflurane-fentanyl-N2O-O2 anesthetic, and for 18 h postoperatively. Normothermic patients were warmed to 36.5-37.0 degrees C after an initial temperature decrease, and hypothermic patients were cooled to 35 degrees C. In the hypothermic group temperatures were allowed to drift to 34.5 degrees C before rewarming was initiated. Water blankets and convective heating devices were used to cool and rewarm. RESULTS: The minimum temperature achieved by the hypothermic group was 34.3 +/- 0.4 degrees C. Cooling occurred at a rate of 1.0 +/- 0.4 degrees C/h. Rewarming took place at a rate of 0.7 +/- 0.6 degrees C/h (range 0.1-1.8) in the hypothermic group. Hypothermia did not delay emergence from anesthesia (20 +/- 15 min) compared with normothermia (15 +/- 15 min, P = .45). Mean temperature upon intensive care unit admission was 35.8 +/- 1.0 degrees C for the hypothermic group and 37.1 +/- 0.5 degrees C for the normothermic group (P < 0.0001). The hypothermic patients had more postoperative shivering. From 8 to 18 h postoperatively the temperatures of the two groups were similar except for a slightly greater temperature in the hypothermic patients at 12 h (37.6 +/- 0.5 vs. 37.3 +/- 0.4 degrees C, P = .029). CONCLUSIONS: Although deliberate mild hypothermia is easily achieved intraoperatively, complete rewarming may be difficult to attain during craniotomy with current methods. In addition to the need for determining whether deliberate mild hypothermia confers cerebral protection in humans, the potential risks of the therapy need to be further characterized.

Aged↗
PubMed1994

Immunoglobulin G enhances C3 degradation on coagulase-negative staphylococci.

Antibody and complement are essential to host defense against infection with coagulase-negative staphylococci in the neonate. To evaluate the influence of antibody on C3 deposition, we compared the C3 fragments deposited on coagulase-negative staphylococci after opsonization with normal human serum or with hypogammaglobulinemic serum. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (immunoblot) analysis, the degradation products of C3 were less apparent at 1 and 2 min after opsonization with hypo- and agammaglobulinemic serum than those from normal human serum. This finding suggested that antibody contained in normal human serum contributes to efficient C3 deposition in the early phases of opsonization. There was no clear difference in C3 deposition when slime-producing strains were compared with non-slime-producing strains. The addition of intravenous immunoglobulin to hypogammaglobulinemic serum and serum from premature neonates rendered C3 deposition comparable to that seen with normal human serum. The data from these experiments suggest that the addition of immunoglobulin G may improve host defense against coagulase-negative staphylococci in the hypogammaglobulinemic premature neonate by enhancing C3 deposition, thus promoting opsonophagocytosis of these bacteria.

Adult↗
PubMed1994

Demonstration of circulating group B streptococcal immune complexes in neonates with meningitis.

Group B streptococci are the major cause of sepsis and fatal shock in neonates in the United States. Although a number of clinical features have been associated with enhanced severity of disease, the role of soluble immune complex formation in group B streptococcal infection has not been evaluated. We determined the frequency with which circulating immune complexes occurred in 16 infants with nonfatal type III, group B streptococcal meningitis, using an immunoglobulin-specific C1q enzyme immunoassay. Ten healthy, age-matched infants served as a control group. Elevated levels of immunoglobulin M (IgM)-containing immune complexes were present in the sera of four (25%) patients with group B streptococcal meningitis. Group B antigen was detected in precipitated IgM immune complexes from each of these four infants by competitive enzyme-linked immunosorbent assay. In addition, IgG-containing immune complexes were present in 56% of sick and 60% of control infants. Group B antigen was demonstrated in the serum of a sick neonate containing only IgG immune complexes but not in controls. Our findings indicate that a subset of infants with type III, group B streptococcal meningitis develop IgM immune complexes containing group B-specific antigen, and these may persist for up to 3 months in some patients.

Antibodies, Bacterial↗
PubMed1994

Stability and activity of intravenous immunoglobulin with neonatal dextrose and total parenteral nutrient solutions.

OBJECTIVE: To determine in vitro the compatibility of reconstituted intravenous immunoglobulin (IVIG) (Gammagard, Baxter-Hyland) with five different neonatal and pediatric intravenous solutions in Viaflex polyvinyl chloride bags. DESIGN: In vitro compatibility study. INTERVENTIONS: Samples were taken at time = 0, 10, 30, 60, 90, and 120 minutes and at 4, 8, 12, and 24 hours and assayed for total immunoglobulin G content and antibodies to hepatitis B surface antigen. Type III group B Streptococcus (GBS) and opsonic activity for type III GBS were analyzed at time = 0, 60, and 120 minutes and 12 and 24 hours. All results were compared with those from pure IVIG. RESULTS: Our results demonstrate that mixing IVIG with intravenous solutions commonly used in the care of premature infants (dextrose 5% in water [D5W], D15W, D5W/NaCl 0.225%, and total parenteral nutrition [TPN]) does not significantly alter total immunoglobulin G concentrations or concentration of antibodies to hepatitis B surface antigen or type III GBS. As well, the in vitro functional activity for type III GBS of the IVIG, when mixed with these solutions for up to 24 hours, remained intact. An apparent decrease in bactericidal killing was seen with the IVIG/central TPN mixture. This apparent decrease was found to be an artifact of the high concentration of glucose (20 percent) in the solution. CONCLUSIONS: We propose that Gammagard may be mixed with these solutions through Y-site connections without loss of antibody content or functional activity of the IVIG.

Antibodies, Bacterial↗
PubMed1994

Effect of mild hypothermia on nitric oxide synthesis during focal cerebral ischemia.

The cerebroprotective effects of mild hypothermia have been extensively studied in various animal models of ischemia, but the mechanism by which mild hypothermia diminishes ischemic injury is not well understood. Nitric oxide (NO) has been implicated as a mediator of glutamate excitotoxicity in primary neuronal cultures, and its synthesis is acutely increased during focal ischemia in vivo. To evaluate possible mechanisms of hypothermic neuroprotection, we measured markers of NO synthesis--nitrite and cyclic guanosine monophosphate (cGMP) levels and NO synthase activity--during right middle cerebral artery occlusion (MCAO) in the rat under normothermic (36.5 degrees C) and mild hypothermic (33 degrees C) conditions. There was a significant increase in nitrite concentration in the right hemisphere versus the left under normothermic conditions at 10 and 20 minutes after MCAO (P < 0.01), with a return to baseline levels by 60 minutes. The increase in cortical nitrite levels in the right hemisphere versus the left was not observed with mild hypothermia. There was a threefold increase in cGMP synthesis in the normothermic right cortex 10 minutes after MCAO (P < 0.05). This rise in cGMP did not occur in hypothermic animals, and the right to left cortical disparity in cGMP production was abolished. Finally, the significant increase in NO synthase activity seen in the normothermic ischemic cortex was absent in hypothermic rats (P < 0.05). These results suggest that mild hypothermia (33 degrees C) modulates the burst of nitric oxide synthesis during cerebral ischemia and may account, at least partially, for its cerebroprotective effects.

Amino Acid Oxidoreductases↗
PubMed1993

Resolution of focal CT hypodense lesions in patients with subarachnoid hemorrhage.

Cerebral infarction in the setting of vasospasm due to subarachnoid hemorrhage (SAH) is a known complication of aneurysmal rupture. Computed tomography (CT) has been instrumental in making this diagnosis; however, focal hypodense lesions on CT scan do not always represent infarcted tissue. Two patients are presented here who had CT hypodense lesions in regions of cerebral vasospasm following subarachnoid hemorrhage.

Adult↗
PubMed1993

Neonatal sepsis caused by a new group B streptococcal serotype.

Two infants with typical clinical presentations for invasive neonatal group B streptococcal disease caused by a new serotype, type V, are described. Organisms of this capsular type should be sought among isolates from sick neonates to evaluate their prevalence and associated patterns of disease.

Bacteremia↗
PubMed1993

Variation in phenotypic expression of the Opa outer membrane protein and lipooligosaccharide of Neisseria meningitidis serogroup C causing periorbital cellulitis and bacteremia.

Expression of the Opa outer membrane protein varies widely among isolates of Neisseria meningitidis; the clinical significance of this variation is unclear. A sialic-acid acceptor is present in the lipooligosaccharide of some strains of Neisseria and has been shown to render Neisseria gonorrhoeae serum-resistant. We report the case of a patient who had an unusual clinical manifestation of infection due to N. meningitidis serogroup C, periorbital cellulitis with concomitant bacteremia. Clinical isolates from the blood and aspirate of the periorbital cellulitis were identical except for the phenotypic expression of the Opa outer membrane protein in the isolate from the periorbital cellulitis and in the lipooligosaccharide phenotype of the sialic-acid acceptor as defined by monoclonal antibodies. We discuss the laboratory and clinical implications of these findings.

Antigens, Bacterial↗
PubMed1993

Study of human immunodeficiency virus resistance to 2'-3'-dideoxyinosine and zidovudine in sequential isolates from pediatric patients on long-term therapy.

Resistance to zidovudine (3'-azido-3'-deoxythymidine) and 2',3'-dideoxyinosine (ddI) has been reported for human immunodeficiency virus (HIV) isolates from adults, but little is known about these drugs in children. A new micrococulture assay was developed for evaluation of drug susceptibility using single-passage HIV isolates cocultured with peripheral blood mononuclear cells from healthy donors. HIV isolates from children treated with zidovudine or ddI were evaluated to define the emergence of resistance to these antiretroviral agents. Four patients were treated with ddI and 3 with zidovudine for > 15 months. There was a > or = 20-fold decrease in susceptibility to ddI for sequential isolates of HIV recovered from 4 patients treated with ddI for 22-31 months and a 4- to 10-fold decrease in susceptibility to zidovudine in 3 patients. HIV isolates from 3 patients treated with ddI or zidovudine alone showed a minor amount of cross-resistance to the other antiretroviral agent. Results indicate the importance of monitoring antiretroviral drug susceptibility of HIV isolates when assessing clinical deterioration in children treated for > 1 year.

Child↗
PubMed1993

The immune response of children to meningococcal lipooligosaccharides during disseminated disease is directed primarily against two monoclonal antibody-defined epitopes.

A human inhibition monoclonal ELISA (HIMELISA) was used to investigate the immune response of infants and children to meningococcal lipooligosaccharide (LOS). Convalescence from disseminated meningococcal disease significantly increased the inhibition by sera of monoclonal antibody (MAb) binding to two of six defined epitopes on the LOS of meningococcal strain 126E, a strain previously shown to express immunogenic LOS epitopes. The inhibited epitopes were defined by MAbs D6A and 6B7, and both were expressed on the 3.6-kDa LOS of strain 126E. The inhibition of the binding of both MAbs by the convalescent sera was similar to that from children who were meningococcal carriers and greater than that by sera obtained from healthy children. These results support the conclusion that the 3.6-kDa LOS molecule of strain 126E expresses two conserved epitopes that are immunogenic in infants and children; this LOS may serve as a vaccine candidate.

Adolescent↗