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Biomedical subjects

S Kaplan

Publications and source records attributed to S Kaplan.

At least 253 records · Page 14Linked to original sources
PubMed1988

Phenotypic and genetic characterization of cytochrome c2 deficient mutants of Rhodobacter sphaeroides.

Rhodobacter sphaeroides mutants lacking cytochrome c2 (cyt c2) have been constructed by site-specific recombination between the wild-type genomic cyt c2 structural gene (cycA) and a suicide plasmid containing a defective cyc operon where deletion of cycA sequences was accompanied by insertion of a KnR gene. Southern blot analysis confirmed that the wild-type cyc operon was exchanged for the inactivated cycA gene, presumably by double-reciprocal recombination. Spectroscopic and immunochemical measurements, together with genetic complementation, established that the inability of these mutants to grow under photosynthetic conditions was due to the lack of cyt c2. The cyt c2 deficient strains reduced photooxidized reaction center complexes approximately 4 orders of magnitude more slowly than the parent strain. The phenotype and characteristics of these mutants were restored when a wild-type cyc operon was introduced on a stable low copy number plasmid. These experiments provide the first genetic evidence for the obligatory role of cyt c2 in wild-type cyclic photosynthetic electron transport in R. sphaeroides. We have also observed that the R. sphaeroides cyt c2 deficient strains spontaneously gave rise to photosynthetically competent pseudorevertants at a frequency which suggests that the cyt c2 independent photosynthetic electron transport which suppresses the phenotype of the cyt c2 deficient strains was the result of a single mutation elsewhere in the genome.

Cytochrome c Group↗
PubMed1988

The antidysrhythmic effect of metoprolol in the epinephrine treated chick embryo.

It was confirmed through electrocardiography that within two hours after epinephrine treatment, four day chick embryos either maintained normal rhythm or developed a severe cardiac dysrhythmia (22/93, 24% dysrhythmic). The ECG dysrhythmia in epinephrine treated embryos were characterized by periods of bradycardia, asystole, and various supraventricular or ventricular dysrhythmias. Within four hours after treatment, dysrhythmic embryos either reestablished normal rhythmicity or died. Electrocardiographic data also demonstrated that metoprolol pretreatment will block epinephrine induced dysrhythmias (0/46, 0% dysrhythmic). We conclude that metoprolol possesses antidysrhythmic properties in the epinephrine treated chick embryo.

Animals↗
PubMed1988

A broad-host-range vector system for cloning and translational lacZ fusion analysis.

A broad-host-range vector system for studying translational fusions was constructed. The region that retains the origin of replication, nic, mob, and rep genes of the broad-host-range plasmid RSF1010 was isolated as either an HincII or a PstI-PvuII restriction fragment. These restriction fragments were ligated to tetracycline, kanamycin, or streptomycin/spectinomycin resistance genes to generate plasmids pUI501, pUI511, pUI504, and pUI506. A functional lacZ gene lacking downstream lac operon sequences together with the lac promoter was constructed from plasmids pMC1871 and pUC18. This lacZ gene was inserted into pUI501 and pUI511 to generate plasmids pUI502, pUI503, pUI512, and pUI513. An oligodeoxynucleotide sequence that carries three unique blunt-end restriction sites was synthesized, annealed, and ligated in frame to the amino-terminal end of the lacZ gene in each of these plasmids. This multiple cloning sequence will allow translational fusions to the lacZ gene in all three reading frames. The stability of these plasmids and the expression of the lacZ gene in both Escherichia coli and Rhodobacter sphaeroides were studied.

Base Sequence↗
PubMed1988

Comparison of the cardiac output and stroke volume response to upright exercise in children with valvular and subvalvular aortic stenosis.

Cardiac output and stroke volume were evaluated in 17 children (mean age 11.5 +/- 3 years) with discrete, membranous subvalvular (Group I, n = 7) and valvular (Group II, n = 10) aortic stenosis during submaximal and maximal (greater than 75% predicted maximal oxygen consumption) upright cycle ergometry. Patients with valvular aortic stenosis were further subdivided on the basis of their aortic valve gradient at rest determined by cardiac catheterization (Group IIA, gradient less than 40 mm Hg; Group IIB, gradient greater than or equal to 40 mm Hg). These patients were matched with 17 control subjects on the basis of age, sex, height and intensity of exercise during maximal exertion. Cardiac and stroke indexes were determined by the acetylene rebreathing method at each exercise level. Stroke volume index in Group I was significantly greater at rest when compared with that in control subjects (69 +/- 13 versus 53 +/- 11 ml/m2, alpha = 0.01, p less than 0.05) and that in patients in Group II (69 +/- 13 versus 47 +/- 12 ml/m2, alpha = 0.01, p less than 0.05). Patients with subvalvular aortic stenosis were unable to increase their stroke volume index from rest to submaximal exercise and also decreased their stroke volume index at maximal exercise levels. In contrast, patients with mild valvular aortic stenosis (Group IIA) displayed a normal exercise response. Patients with severe valvular aortic stenosis (Group IIB) had a blunted stroke volume response at rest and at each level of exercise, as well as signs of myocardial ischemia (ST segment depression) during maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

A randomized comparison of doxifluridine and fluorouracil in colorectal carcinoma.

In a randomized study 52 patients with advanced colorectal cancer and measurable lesions were treated with doxifluridine 4000 mg/m2 or fluorouracil 450 mg/m2 i.v. on 5 consecutive days over 3 weeks. None had prior fluoropyrimidines except two who received adjuvant fluorouracil. Partial responses with a duration ranging from 259 to 406 days were observed in five patients treated with doxifluridine and two patients treated with fluorouracil. Toxic reactions were evaluated in 88 doxifluridine courses and 105 fluorouracil courses. The most frequent adverse effects were neurotoxicity (48% of patients) and mucositis (43%) for doxifluridine, leukopenia (48%) and nausea/emesis (37%) for fluorouracil. Mucositis, diarrhea, nausea, emesis and skin reactions were observed in both treatment groups. Fluorouracil produced neurotoxic effects in 26% of patients. Reversible cardiac dysfunctions were observed in four patients treated with doxifluridine, expressed by ectopic ventricular beats (2) precordial pains (1) and ventricular fibrillation (1). This latter toxicity justified the premature interruption of the study. Doxifluridine is an active agent in colorectal cancer. Compared to fluorouracil it produces, when used i.v., a lower myelosuppression and a greater incidence of neurological and cardiac toxicity.

Adenocarcinoma↗
PubMed1988

Hypertrophic cardiomyopathy in infants of diabetic mothers: an update.

Infants of diabetic mothers (IDMs) are at known risk for developing a hypertrophic type of cardiomyopathy. The severity of IDM cardiomyopathy can vary from an incidental finding on echocardiography to an infant with severe symptoms of congestive heart failure. The purpose of this article is to review the pathophysiologic mechanisms involved in the development of cardiomyopathy in IDMs and to discuss the diagnostic tests utilized in making the diagnosis (especially echocardiography) and the potential mechanisms that may result in congestive heart failure. This report will conclude with a review of a 2 1/2 year prospective study of diabetic women who had carefully maintained diabetic control during pregnancy. Although the IDMs in this study continued to have mild evidence of generalized hypertrophy when compared with control newborn infants, none developed symptoms of congestive heart failure. These data support the contention that careful diabetic management in pregnancy reduces the severity of hypertrophic cardiomyopathy in IDMs.

Cardiomegaly↗
PubMed1988

Construction, characterization, and complementation of a Puf- mutant of Rhodobacter sphaeroides.

A Puf- strain of Rhodobacter sphaeroides (PUFB1) was constructed by deleting a portion of the proximal region of the puf operon and inserting a kanamycin resistance gene cartridge. Southern blot analysis demonstrated that in PUFB1, the defective copy of the puf operon had replaced, through homologous recombination, the normal chromosomal copy. The Puf- phenotype was characterized by the inability of PUFB1 to grow photoheterotrophically (PS-), the lack of detectable puf-specific transcripts, the absence of the light-harvesting I complex and, by inference, the reaction center spectral complex, and greatly reduced levels of the light-harvesting II complex. The PS+ phenotype was restored to PUFB1 when a 13-kilobase BamHI restriction endonuclease fragment containing the entire puf operon and flanking regions was cloned into the broad-host-range plasmid vector RK2 derivative pRK404 and introduced by conjugation into PUFB1. In these complemented strains, there was an increased number of copies of the puf operon (four to six copies per defective chromosomal copy) as the result of plasmid copy number. However, there was no concomitant increase in either the specific bacteriochlorophyll content or the level of puf-specific transcripts when these strains were grown photoheterotrophically.

Cloning, Molecular↗
PubMed1988

In vivo analysis of puf operon expression in Rhodobacter sphaeroides after deletion of a putative intercistronic transcription terminator.

The intercistronic region of the mRNA derived from the puf operon of Rhodobacter sphaeroides is capable of forming two stable stem-loop structures, the first of which resembles a factor-independent transcription terminator. A puf operon construction lacking the putative transcription terminator was made in vitro and crossed into the chromosome of R. sphaeroides PUFB1 to yield a single chromosomal copy in the terminator-deleted strain. The mutant strain, designated PUF delta 348-420 which was otherwise isogenic with the wild-type strain 2.4.1, showed a normal growth rate at high light intensity compared with the wild type, with the levels of the B875 and reaction center spectral complexes being approximately 7% and 25%, respectively, of those found in the wild type. The deletion mutation correlated with a reduction in the size of the fixed photosynthetic unit from 15:1 in the wild type to 4:1 in the mutant. The level of the B800-850 complex was increased approximately twofold in the mutant strain. However, substantial amounts of the B875 and reaction center polypeptides were not incorporated into spectrally active complexes, suggesting the importance of other factors in the assembly of these complexes. Removal of the intercistronic stem-loops resulted in increased readthrough of the puf operon terminator to regions downstream, as well as altering the stability of the resulting puf operon-specific transcripts. A model is proposed which links ribosome stalling within the open reading frame K leader region of the puf operon transcript with chain termination.

Bacteria↗
PubMed1988

Physiological and structural analysis of light-harvesting mutants of Rhodobacter sphaeroides.

Two mutants of Rhodobacter sphaeroides defective in formation of light-harvesting spectral complexes were examined in detail. Mutant RS103 lacked the B875 spectral complex despite the fact that substantial levels of the B875-alpha polypeptide (and presumably the beta polypeptide) were present. The B800-850 spectral complex was derepressed in RS103, even at high light intensities, and the growth rate was near normal at high light intensity but decreased relative to the wild type as the light intensity used for growth decreased. Mutant RS104 lacked colored carotenoids and the B800-850 spectral complex, as well as the cognate apoproteins. This strain grew normally at high light intensity and, as with RS103, the growth rate decreased as the light intensity used for growth decreased. At very low light intensities, however, RS104 would grow, whereas RS103 would not. Structural analysis of these mutants as well as others revealed that the morphology of the intracytoplasmic membrane invaginations is associated with the presence or absence of the B800-850 complex as well as of carotenoids. A low-molecular-weight intracytoplasmic membrane polypeptide, which may play a role in B800-850 complex formation, is described, as is a 62,000-dalton polypeptide whose abundance is directly related to light intensity as well as the absence of either of the light-harvesting spectral complexes. These data, obtained from studies of mutant strains and the wild type, are discussed in light of photosynthetic membrane formation and the abundance of spectral complexes per unit area of membrane. Finally, a method for the bulk preparation of the B875 complex from wild-type strain 2.4.1 is reported.

Bacterial Proteins↗
PubMed1988

Urban community reaction to health facilities in residential areas: lessons from the placement of methadone facilities in New York City.

Neighborhood characteristics associated with negative reaction to community-based methadone maintenance treatment programs (MMTPs) were studied using the MMTPs in Brooklyn, Bronx, Manhattan, and Queens (71 census tracts). A measure of community opposition to the establishment of the clinics was developed (CRMC). Census and survey data were combined for data analysis. Results are presented following a fourfold conceptual framework focused on the community's social ecology, patient characteristics, clinic administration, and the physical ecology of the clinic location. Eight specific characteristics found within these four conceptual areas accounted for 49% of the variation in CRMC.

Community-Institutional Relations↗
PubMed1988

The laser: an alternative for palliative treatment of obstructing intraluminal lesions.

Twenty nine patients with carcinoma obstructing the colon, six obstructing the gastroesophageal junction, six obstructing the tracheobronchial tree, and one patient with recurrent transitional cell cancer of the bladder invading the rectum, not amenable to surgical resection, were treated by laser photocoagulation. Forty were treated with the Nd:YAG laser and two with the CO2 laser. There were 26 men and 16 women with an average age of 73.8 years. The locations of the tumors were 17 rectal, six rectosigmoid, one transverse colon, two descending colon, four ascending colon, six gastroesophageal, and six in the tracheobronchial tree. Symptoms consisted of obstruction and/or bleeding. Seventeen patients were poor surgical candidates, 25 were unresectable due to widespread disease, two had recurrence at the anastomosis, and three patients had another primary site not controlled by their previous surgical procedure. There were seven complications--three perforations, a rectovaginal fistula, two failures in therapy, and lower GI bleeding. Nineteen patients have died of their disease. Tumors were eradicated in two patients. Forty patients had remained free of referring symptoms of obstruction and bleeding.

Adenocarcinoma↗
PubMed1988

Relationships among dental functional status, clinical dental measures, and generic health measures.

Current measures of dental health status are primarily clinical in nature and rely on clinical and radiographic assessment of the patient's dental health. Information about a patient's ability to perform usual activities related to good dental health--for example, chewing, speaking, and smiling--is not routinely collected. This study investigated what measures contribute to dental functional status, how they are related to traditional clinical measures, whether dental factors contribute to other generic measures of health, and the extent to which dental factors contribute to overall quality of life. Regression analyses of interview and clinical data from 159 dental patients show that while periodontal status and the number of dental symptoms do explain some of dental functional status, the clinical measures of decayed, missing, and filled teeth do not. Severity of medical condition is correlated with decayed/missing teeth and periodontal health. Quality of life is explained by medical functional status, perceived medical health, and perceived dental health. The dental functional status index may be useful in clarifying the relationship between dental health and overall health and quality of life measures.

Adult↗
PubMed1988

Small bowel transplantation in the rat. Effect of pretransplant blood transfusions and cyclosporine on host survival.

We investigated the effect of pretransplant conditioning as a way to reduce the need for the aggressive immunosuppressive therapy reportedly required in small bowel (SB) allograft recipients. LEW rats were conditioned with (1) a donor-specific blood transfusion (DST) on day -8 and a concurrent 5-day course of CsA (10 mg/kg/day); (2) a nonspecific blood transfusion and CsA; (3) CsA alone. A 10-cm segment of the host native bowel was then replaced with an equivalent segment of SB obtained from ACI rats. Postoperative treatment consisted of CsA at 2.5 mg/kg/day for 30 days. Rats conditioned with a nonspecific transfusion and CsA or with CsA alone survived for 14.1 +/- 5.8 and 18.3 +/- 5.7 days, respectively. In contrast, rats conditioned with DST and CsA survived for 60.3 +/- 36.2 days (P less than 0.001 vs. both controls). Biopsies taken from long-term survivors showed a normal bowel architecture. The function of the allografts was studied in a group of animals totally deprived of their native bowel and transplanted with a 30-cm segment of ACI SB. CsA-DST-treated recipients survived an average of 90 +/- 43 days and grew at a rate comparable to isografted animals. Treated allograft recipients had maltose absorption indistinguishable from isografted controls at all times tested. In contrast, maltose absorption was severely impaired in recipients rejecting their grafts. This study demonstrates that long-term survival of SB allograft recipients can be achieved with good functional results with low doses of CsA in recipients conditioned with DST and CsA.

Animals↗
PubMed1987

On the role of the light-harvesting B880 in the correct insertion of the reaction center of Rhodobacter capsulatus and Rhodobacter sphaeroides.

The purple, non-sulfur photosynthetic bacteria Rhodobacter capsulatus and Rhodobacter sphaeroides have two types of pigment-protein complexes that absorb incident light and funnel it to the photochemical reaction center. One of these, B880, is present at an essentially constant ratio to the reaction center, while the abundance of the other, B800-850, varies with growth conditions. Independent work in our two laboratories has indicated that while the absence of B800-850 permits photosynthetic growth in both organisms, the lack of B880 produces a different phenotype in the two species. Thus R. sphaeroides is still photosynthetically competent when it lacks this complex, while R. capsulatus is not. This unanticipated difference in what appear to be very closely related organisms has caused us to reexamine the properties of the two mutants simultaneously, under identical conditions. We find that the original descriptions are indeed correct; the reaction center of R. capsulatus is not correctly inserted into the photosynthetic membrane in the absence of B880, while that of R. sphaeroides is.

Bacterial Proteins↗
PubMed1987

Plasma norepinephrine levels in infants and children with congestive heart failure.

To characterize the sympathetic nervous system response to congestive heart failure (CHF) in infants and children, plasma catecholamine levels were measured in 102 subjects undergoing routine cardiac catheterization (mean age 3.3 years, range 0.1 to 14.7), including 61 with left-to-right shunts. Plasma norepinephrine levels were significantly higher (p less than 0.0001) in children with CHF than in those without CHF. A highly significant association (p less than 0.0001) was found between the level of plasma norepinephrine and severity of CHF symptoms. This relation was found for CHF secondary to lesions producing a left-to-right shunt and CHF resulting from primary myocardial dysfunction. In congenital lesions with a left-to-right shunt, plasma norepinephrine levels correlated well with size of the shunt (Qp/Qs) (r = 0.75, p less than 0.001) and degree of pulmonary arterial hypertension (r = 0.70, p less than 0.001). Elevation of plasma norepinephrine concentrations in infants and children are seen with severe CHF regardless of its origin.

Adolescent↗