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Biomedical subjects

S Kaplan

Publications and source records attributed to S Kaplan.

At least 217 records · Page 12Linked to original sources
PubMed1991

Laser resistant stainless steel endotracheal tube: experimental and clinical evaluation.

A fire due to endotracheal tube (ET) ignition is a catastrophic event that may occur during laser surgery of the upper airway, regardless of the wavelength utilized. Although methods exist that permit laser surgery without an ET, this is frequently not feasible. The current investigation was undertaken to evaluate the efficacy of a double-cuffed stainless steel ET, first in the laboratory and subsequently in a clinical setting. Bench testing was performed using CO2 (both standard and milliwatt) and KTP/532 lasers. Only the distal polyvinyl chloride cuffed end of the tube was potentially ignitable, however, the appropriate use of saline to fill the cuffs allowed only for cuff perforation without ignition. Canine testing was performed in 10 animals: 4 dogs were intubated from 3 to 4.5 hours with the laser resistant stainless steel endotracheal tube (LRSS-ET) (Laser-Flex Tracheal Tube; Mallinckrodt Anesthesia Products, St. Louis, MO) and 2 with an aluminum tape wrapped red rubber ET. Visual and histological examination were performed in both groups at 3 and 7 days. Four dogs underwent CO2 laser laryngeal surgery with visual and histological examination performed at 7 days postoperatively. No untoward effects could be demonstrated due to the LRSS-ET. A clinical study was then performed in 24 patients who underwent laser surgery of the upper aerodigestive tract with either a CO2 or KTP/532 laser. In all cases ventilation was adequate, the shaft of the LRSS-ET proved impervious to the laser, and the distal end of the tube protected the tracheobronchial tree safely.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Left ventricular mass in childhood dilated cardiomyopathy: a possible predictor for selection of patients for cardiac transplantation.

To determine the relationship of left ventricular hypertrophy (as assessed by mass) to symptoms and cardiac function in chronic childhood dilated cardiomyopathy, 17 long-term survivors (12 asymptomatic, 5 symptomatic) were studied at a median follow-up of 6.25 years (1.25 to 16.8 years). Left ventricular mass, dimension, wall stress, and contractility (relationship between velocity of circumferential fiber shortening and end-systolic wall stress) were assessed by echocardiography. These data were compared to measurements at the onset of disease. At follow-up, mass decreased significantly from the onset in the asymptomatic patients but remained elevated in the symptomatic patients (101 +/- 35 gm/m2 to 54 +/- 12 gm/m2, p = 0.001; 122 +/- 55 gm/m2 to 198 +/- 115 gm/m2, p = 0.23, respectively). Shortening fraction and contractility were both significantly lower in the symptomatic group compared with the asymptomatic group at follow-up (shortening fraction = 21 +/- 7% vs 29 +/- 5%, p = 0.02; contractility = -0.24 +/- 0.14 circ/sec vs -0.05 +/- 0.11 circ/sec, p = 0.01). Follow-up wall stress was slightly higher in symptomatic patients compared with asymptomatic patients. Three symptomatic patients had progressive hypertrophy and either died or required transplantation. Higher left ventricular mass is associated with the presence of symptoms, depressed contractility, and slightly higher wall stress. Persistence or progression of hypertrophy may be a poor prognostic sign in survivors of childhood dilated cardiomyopathy. Measurement of mass may be useful to indicate the necessity for closer follow-up to select patients for cardiac transplantation before hemodynamic decompensation.

Cardiomegaly↗
PubMed1991

Genetic and physical mapping of the Rhodobacter sphaeroides photosynthetic gene cluster from R-prime pWS2.

Plasmid pWS2 is an R68.45 chimera originally isolated as an R-prime which complemented the Rhodobacter sphaeroides bch-420 allele. Our experiments have shown that pWS2 is also able to complement a wide range of R. sphaeroides pigment and photosynthetic mutants employing nitrosoquanidine, transposon or insertion-generated mutations effecting puhA, puc, puf, cycA, bch, and crt genes. A combination of orthogonal-field-alternation gel electrophoresis, transverse alternating field gel electrophoresis, and conventional electrophoresis have been used to estimate the size of pWS2 at congruent to 168.3 +/- 3.5 kb. A restriction map of the congruent to 109 kb of R. sphaeroides insert DNA was generated by partial and complete restriction endonuclease digestion coupled with Southern hybridization analysis using either gene-specific or junction fragment probes. Genes encoding bacteriochlorophyll (Bchl)-binding proteins (pufBALMX, pucBA, and puhA), cytochrome c2 (cycA), and enzymes involved in Bchl (bch) and carotenoid (crt) biosynthesis have been shown to reside within a contiguous 53-kb region of the R. sphaeroides DNA present on pWS2. The puf operon lies at one end of the 53-kb segment, while the genes puhA, cycA, and pucBA, the latter two of which are located within congruent to 12.0 kb of each other, define the other end of this 53-kb region. The genetic and physical mapping data provided in this paper are discussed in terms of the similarities and differences in the organization of the photosynthetic gene cluster between R. sphaeroides and other photosynthetic bacteria as well as highlighting the use of pWS2 in studies of photosynthetic gene structure and function.

Blotting, Southern↗
PubMed1991

Gender identification and sex role attribution in sexually abused adolescent females.

An exploratory study of the association between child sexual abuse and subsequent gender identification and sex role attribution was conducted with 93 adolescent females. Victims of intrafamilial sexual abuse with a history of psychotherapeutic treatment were compared with nonabused subjects with a history of treatment and nonabused control subjects with no treatment history. Measures of gender identity found that sexually abused and nonabused treatment groups differed significantly from the no-treatment controls. Distinct patterns of gender identification emerged for the sexually abused victims. Hypothesized differences in sex role attribution were not found. Potential directions for future research are proposed and implications and recommendations for treatment are discussed.

Adolescent↗
PubMed1991

A randomized clinical trial of ampicillin, gentamicin and clindamycin versus cefotaxime and clindamycin in children with ruptured appendicitis.

This prospective, randomized, double-blind study compares the efficacy, safety and cost-effectiveness of ampicillin, gentamicin and clindamycin (AGC) or cefotaxime and clindamycin (CC) for the treatment of children with complicated appendicitis. Ninety-seven children were randomized. Forty-seven were assigned to the AGC regimen and 50 received CC. Forty-two patients in the AGC group had an appropriate therapeutic outcome, whereas 48 of 50 children who received CC completed the trial successfully (p = NS). There were no differences between the groups with reference to the duration of antibiotic administration, fever, leukocytosis or length of hospitalization. Complications of therapy were uncommon and neither regimen demonstrated a significant advantage from an economic standpoint. We concluded that, in childhood, complicated appendicitis can be treated with either CC or AGC with equal efficacy.

Adolescent↗
PubMed1991

A comparative study of contrast agents for endoscopic retrograde pancreatography.

Pancreatitis is a major cause of morbidity and mortality secondary to endoscopic retrograde pancreatography (ERP). One factor that may cause post-ERP pancreatitis is the type of contrast media utilized during the procedure. The purpose of this prospective, double-blind, randomized study was to evaluate the effects of three contrast agents of differing osmolality and ionicity on changes between pre- and post-ERP chemical changes in serum amylase and lipase and development of clinical symptoms of acute pancreatitis. Our study of 53 patients showed that those who received Omnipaque a non-ionic, relatively iso-osmolar contrast agent, had a significantly lower serum amylase (p = 0.0038) and serum lipase (p = 0.0002) in post-ERP serological markers, compared with patients who received the ionic agents, Hypaque meglumine 60% or Hexabrix. In addition, the development of clinical symptoms of pancreatitis was less in patients who received Omnipaque than in those who received Hexabrix or Hypaque (1 vs. 3 vs. 4). No significant difference was found between patients who received ionic agents. No patient who received Omnipaque needed hospitalization, whereas one (6%) patient who received Hexabrix was hospitalized compared to three (20%) hospitalized patients who received Hypaque. When the initial cost and cost of hospitalization were compared, the non-ionic contrast medium was also found to be more cost-effective for the patient. In summary, the risk of post-ERP acute pancreatitis was significantly lower for patients who received the non-ionic contrast agent than for those who received the ionic agents.

Adolescent↗
PubMed1990

Localization and structural analysis of the ribosomal RNA operons of Rhodobacter sphaeroides.

We have identified, cloned and sequenced the three ribosomal RNA (rRNA) operons (rrn) present in the facultative photoheterotroph Rhodobacter sphaeroides. DNA sequence analysis has identified the 16S, 23S, and 5S rRNAs, two tRNAs (ile and ala) in the spacer region between the 16S and 23S rRNAs, and an f-met tRNA immediately following the 5S rRNA gene of all three operons. Physical mapping, genetic analysis, and Southern hybridization data indicate that rrnA is contained on a large chromosome and rrnB and rrnC are contained on a second smaller chromosome. These findings are discussed in relation to the origins of diploidy.

Base Sequence↗
PubMed1990

Cloning and DNA sequencing of the fbc operon encoding the cytochrome bc1 complex from Rhodobacter sphaeroides. Characterization of fbc deletion mutants and complementation by a site-specific mutational variant.

The ubiquinol: cytochrome-c oxidoreductase (cytochrome bc1 complex) is a central component of the mitochondrial respiratory chain as well as the respiratory and/or photosynthetic systems of numerous prokaryotic organisms. In Rhodobacter sphaeroides, the bc1 complex has a dual function. When the cells are grown photosynthetically, the bc1 complex is present in the intracytoplasmic membrane and is a critical component of the cyclic electron transport system. When the cells are grown in the dark in the presence of oxygen, the same bc1 complex is a necessary component of the cytochrome-c2-dependent respiratory chain. The fact that the bc1 complex from R. sphaeroides has been extensively studied, plus the ability to manipulate this organism genetically, makes this an ideal system for using site-directed mutagenesis to address questions relating to the structure and function of the bc1 complex. In the current work, the cloning and complete sequence of the fbc operon from R. sphaeroides is reported. As in other bacteria, this operon contains three genes, encoding the Rieske 2Fe-2S subunit, the cytochrome b subunit, and the cytochrome c1 subunit. Recombination techniques were used to delete the entire fbc operon from the chromosome. The resulting strain cannot grow photosynthetically, but can grow aerobically utilizing a quinol oxidase. Photosynthetic growth is restored by providing fbc operon on a plasmid, and the reappearance of the protein subunits and the spectroscopic features due to the bc1 complex are also demonstrated. Finally, a mutation is introduced within the gene encoding the cytochrome b subunit which is predicted to confer resistance to the inhibitor myxothiazol. It is shown that the resulting strain contains a functional bc1 complex which, as expected, is resistant to the inhibitor. Hence, this system is suitable for the detailed characterization of the bc1 complex, combining site-directed mutagenesis with the biochemical and biophysical techniques which have been previously developed for the study of photosynthetic bacteria.

Amino Acid Sequence↗
PubMed1990

Implant site: a determinant of completeness of arterial prosthesis healing in the dog and possibly in humans.

This paper compares the healing of supported knitted Dacron prostheses implanted in the descending thoracic aorta and in the subcutaneous carotid-femoral positions in each of 10 dogs. The descending thoracic aorta prostheses were 6 cm long and the carotid-femoral prostheses averaged 76 cm in length. The healing of four porous clinical axillofemoral grafts is compared to that of the experimental carotid-femoral grafts. There was little similarity between the healing observed in the descending thoracic aortic and subcutaneous positions; the descending thoracic aorta grafts healed rapidly and completely by eight weeks, with thrombus-free flow surfaces covered with confluent endothelial cells. However, the inner wall of the carotid-femoral grafts remained largely unhealed at one year, with endothelialization largely confined to a limited pannus ingrowth across the anastomoses. This indicates that the implant site in the dog is a primary determinant of the rapidity and completeness of healing. The clinical axillofemoral grafts explanted after 20 months to six and one-half years exhibited healing characteristics that were similar to those seen in the carotid-femoral position in the dog. These findings suggest that valid comparisons of interspecies healing require data obtained from similar implant locations. They present a challenge to the previously held concepts of major interspecies differences in speed and extent of tissue ingrowth based on data obtained from noncomparable implant sites.

Animals↗
PubMed1990

The evolution of a clinically relevant experimental model for the realistic evaluation of long-length (80-cm) arterial prostheses.

A new carotid-femoral experimental model has been developed which has significant clinical relevance to human limb salvage bypass grafting in the areas of graft length, hemodynamics and tissue environment. More significantly, the graft healing pattern observed with this model is similar to what is seen in humans. Therefore, this experimental model provides a challenging and critical site for dynamic healing studies and comparisons of different types of vascular prostheses.

Animals↗
PubMed1990

Roles of CfxA, CfxB, and external electron acceptors in regulation of ribulose 1,5-bisphosphate carboxylase/oxygenase expression in Rhodobacter sphaeroides.

The Rhodobacter sphaeroides genome contains two unlinked genetic regions each encoding a series of proteins involved in CO2 fixation which include phosphoribulokinase (prkA and prkB) and ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcLS and rbcR) (P. L. Hallenbeck and S. Kaplan, Photosynth. Res. 19:63-71, 1988; F. R. Tabita, Microbiol. Rev. 52:155-189, 1988). We examined the effect of CO2 in the presence and absence of an alternate electron acceptor, dimethyl sulfoxide, on the expression of rbcR and rbcLS in photoheterotrophically grown R. sphaeroides. The expression of both rbcR and rbcLS was shown to depend on the CO2 concentration when succinate was used as the carbon source. It was also demonstrated that CO2 fixation is critical for photoheterotrophic growth but could be replaced by the alternative reduction of dimethyl sulfoxide to dimethyl sulfide. Dimethyl sulfoxide severely depressed both rbcR and rbcLS expression in cells grown photoheterotrophically at CO2 concentrations of 0.05% or greater. However, cells grown photoheterotrophically in the absence of exogenous CO2 but in the presence of dimethyl sulfoxide had intermediate levels of expression of rbcL and rbcR, suggesting partially independent control by limiting CO2 tension. We also present evidence for the existence of two gene products, namely, CfxA and CfxB, which are encoded by genes immediately upstream of rbcLS and rbcR, respectively. Strains were constructed which contained null mutations in cfxA and/or cfxB. Each mutation eliminated expression of the linked downstream rbc operon. Further, studies utilizing these strains demonstrated that each form of ribulose 1,5-bisphosphate carboxylase/oxygenase plays an essential role in maintaining the cellular redox balance during photoheterotrophic growth at differing CO2 concentrations.

Carbon Dioxide↗
PubMed1990

Phosphoribulokinase activity and regulation of CO2 fixation critical for photosynthetic growth of Rhodobacter sphaeroides.

The Rhodobacter sphaeroides genome contains two unlinked genetic regions each encoding numerous proteins involved in CO2 fixation which include phosphoribulokinases (prkA and prkB), ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcLS and rbcR) (P. L. Hallenbeck and S. Kaplan, Photosynth. Res. 19:63-71, 1988; F. R. Tabita, Microbiol. Rev. 52:155-189, 1988), and two open reading frames linked to rbcLS and rbcR, namely, cfxA and cfxB, respectively (P. L. Hallenbeck, R. Lerchen, P. Hessler, and S. Kaplan, J. Bacteriol. 172:1736-1748). In this study, we examined the unique role(s) of each phosphoribulokinase activity in the regulation of CO2 fixation. Strains were constructed which contain null mutations in prkA and/or prkB. Studies utilizing these strains suggested that CO2 fixation plays an essential role in attaining the cellular redox balance necessary for photoheterotrophic growth. The presence of an external electron acceptor can negate the requirement for CO2 for photoheterotrophic growth. Each form of phosphoribulokinase and ribulose 1,5-bisphosphate carboxylase/oxygenase was shown to have distinct roles in CO2 metabolism when cells were exposed to extremes in CO2 levels. Evidence is also presented which unequivocally demonstrated that regulation of the expression of the enzymes involved in CO2 metabolism is effective at the transcriptional level. Although the two regions of the DNA involved in CO2 fixation are physically unlinked, each region of the DNA can have a profound effect on the expression of the other region of the DNA.

Carbon Dioxide↗
PubMed1990

New drug approaches to the treatment of heart failure in infants and children.

General considerations in planning therapy of heart failure include identification of the cause, rapidity of onset, and the age of the patient. Neonates and young infants with acute onset heart failure frequently develop acidaemia, respiratory compromise or failure, and metabolic derangements such as hypoglycaemia, hypocalcaemia or hypomagnesaemia. These complications require early recognition and urgent therapy. The diagnosis of heart failure in neonates with ductal dependent congenital cardiac lesions (such as coarctation of the aorta, hypoplastic left heart syndrome or pulmonary valve atresia) allows the early institution of alprostadil (prostaglandin E1) therapy to maintain patency of the ductus arteriosus, which stabilises these infants before surgical therapy. Classic therapy for infants with heart failure due to a large left-to-right shunt consists of salt restriction, diuretics and digoxin. If this treatment is inadequate an angiotensin converting enzyme (ACE) inhibitor (e.g. captopril) is added to therapy. The question then arises whether captopril and diuretics should be the initial therapy and digoxin added if this treatment fails. Acute heart failure may occur in the immediate postoperative period after cardiac surgery or may complicate acute overwhelming infections. Therapy consists of volume loading, vasodilator or inotropic agents. Heart failure due to various forms of chronic dilated cardiomyopathy usually responds to treatment with salt restriction, diuretics, digoxin and captopril. Acute deterioration requires treatment with vasodilators and/or inotropic agents. Heart failure in fetuses may occur from sustained supraventricular tachyarrhythmias, and may respond to treatment of the mother with antiarrhythmic agents such as digoxin or procainamide.

Arrhythmias, Cardiac↗
PubMed1990

Re-endothelialization of isolated segments of the canine carotid artery with reference to the possible role of the adventitial vasa vasorum.

This study was designed to determine if the adventitial vasa vasorum contribute to re-endothelialization of the canine carotid artery after removal of the endothelial flow surface. Casting studies demonstrated that vasa vasorum are present only in the adventitia of the canine carotid artery. Ninety autograft segments of the carotid artery from which the endothelium had been removed were implanted in both carotid arteries of 45 dogs. Glutaraldehyde-processed canine carotid allografts were positioned at each end to prevent pannus ingrowth and a Gore-Tex wrap to prevent periarterial tissue growth was placed into the outer wall. Three methods were used, with observations at 4 and 8 weeks. In method 1 the test segment was treated with superficial endarterectomy. In method 2 a balloon catheter was used to remove the endothelium. In method 3 balloon catheter denudation of the flow surface was also employed and, in addition, the adventitia was removed surgically as completely as possible, although a few vasa vasorum were shown to remain in some grafts. In method 1 all the patent endarterectomized arteries were partially re-endothelialized at both the 4- and 8-week intervals. In method 2, 72% of the balloon-denuded patent arteries with intact adventitial vasa vasorum were partially re-endothelialized at 4 weeks and 84% at 8 weeks. However, in method 3 the flow surfaces had no endothelium at 4 weeks and 83% still had none at 8 weeks. These findings suggest that, in the absence of pannus ingrowth, re-endothelialization of the canine carotid artery depends on not only the presence but also the number of adventitial vasa vasorum.

Animals↗
PubMed1989

Transcriptional analysis of puf operon expression in Rhodobacter sphaeroides 2.4.1 and an intercistronic transcription terminator mutant.

DNA sequence analysis of the pufX region, the most distal gene of the pufBALMX operon of Rhodobacter sphaeroides, revealed a sequence encoding a putative polypeptide of 82 amino acids with a molecular mass of 9052 Da followed by a puf operon-specific transcription terminator. Analysis of the 5' and 3' termini of the transcripts produced in vivo from the puf operon of R. sphaeroides PUF delta 348-420 (three transcripts; 0.59, 0.64, and 2.63 kilobases) lacking the puf-intercistronic terminator structure were identical to those of the corresponding puf transcripts derived from wild-type R. sphaeroides 2.4.1 (four transcripts; 0.50, 0.66, 0.71, and 2.7 kilobases) showing that the transcripts begin and end at the same sites. However, the absence of the puf intercistronic terminator resulted in both the loss of the smallest transcript found in wild type and increased transcriptional read-through of the mutated region to the more distal pufL gene, supporting our previous contention that the proximal intercistronic stem-loop functions as a transcription terminator. The 5' terminus of the medium sized puf transcript has been localized to the same site as that of the small puf transcript. These analyses also showed conclusively that the puf operon-specific transcripts are not extended transcripts derived from the upstream open reading frame Q. In addition, a 120-nucleotide RNA was detected which encompassed the terminator region downstream of pufX and extended into the next downstream open reading frame. The 120-nucleotide RNA of unknown function was regulated by O2 and is unique in its abundance and stability. By comparison with strain 2.4.1, the mutant PUF delta 348-420 showed an increased amount (1.9-fold) of the 120-nucleotide RNA, suggesting that its synthesis is under the control of the puf operon despite the fact that its sequence appears to overlap the next downstream operon.

Amino Acid Sequence↗