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Biomedical subjects

M Jacobs

Publications and source records attributed to M Jacobs.

At least 127 records · Page 7Linked to original sources
PubMed1994

Membrane binding properties of the factor IX gamma-carboxyglutamic acid-rich domain prepared by chemical synthesis.

The fully gamma-carboxylated peptides based upon the complete and truncated Gla/aromatic amino acid stack domains of human Factor IX were prepared by solid phase peptide synthesis using Fmoc (N-(9-fluorenyl)methoxycarbonyl) chemistry. A 47-residue peptide Factor IX-(1-47) and a 42-residue peptide Factor IX-(1-42), both containing 12 residues of L-gamma-carboxyglutamic acid, were purified by high performance liquid chromatography and oxidized to form the disulfide bond. Quantitative gamma-carboxyglutamic acid analysis of Factor IX-(1-47) and Factor IX-(1-42) indicated the presence of 12.1 and 11.2 gamma-carboxyglutamic acid residues/mol of peptide, respectively; no glutamic acid was detected. As monitored by fluorescence quenching, calcium ions induced the prototypical conformational transition in Factor IX-(1-47), but not in Factor IX-(1-42), that is observed with Factor IX. Half-maximal quenching of the intrinsic fluorescence of Factor IX-(1-47) was observed at Ca(II) concentrations of about 50 microM. Factor IX-(1-47) bound to the conformation-specific antibodies, anti-Factor IX:Mg(II) and anti-Factor IX:Ca(II)-specific in the presence of metal ions. Factor IX-(1-47) bound to phospholipid membranes, as monitored by energy transfer from intrinsic fluorophores to dansyl (5-dimethylaminonaphthalene-1-sulfonyl)-phosphatidylethanolamine incorporated into a lipid bilayer composed of phosphatidylserine:phosphatidylcholine. In contrast, Factor IX-(1-42) bound poorly to these same membranes. Factor IX-(1-47) did not inhibit Factor XIa activation of Factor IX but did inhibit the activation of Factor X by Factor IXa bound to Factor VIII in the presence of calcium ions and phospholipid. These results show that phospholipid membrane binding is a property of the Gla/aromatic amino acid stack domain and that the Factor IX-(1-47) peptide, prepared by chemical synthesis, preserves the membrane binding properties and the metal-induced conformational transitions observed in native Factor IX. These results indicate that Factor IX-(1-47) but not Factor IX-(1-42) is a suitable model for structural studies of Factor IX-membrane interaction.

1-Carboxyglutamic Acid↗
PubMed1994

Sequential psychomotor skills development in laparoscopic colon surgery.

OBJECTIVES: To quantify the complexity of each of three skills used in laparoscopic colon surgery and to quantify the relative complexity of seven laparoscopic colon procedures on a graduated complexity scale. DESIGN: Five surgeons used a scale of 1 through 6 to measure the relative complexity of three laparoscopic skills (intracorporeal mobilization, intracorporeal devascularization, and intracorporeal anastomosis) to assess the relative difficulty of seven laparoscopic procedures (right colon resection, sigmoid colon resection, low anterior resection, Hartmann's procedure, left colon resection, abdominoperineal resection, and transverse colon resection) using detailed evaluation of their first 100 laparoscopic colon resections. SETTING: Three private community hospitals. MAIN OUTCOME MEASURES: The complexities of intracorporeal mobilization, intracorporeal devascularization, and intracoporeal anastomosis were recorded for seven laparoscopic colon procedures. RESULTS: The least complex procedure was right colon resection, followed in increasing complexity by sigmoid colon, Hartmann's procedure, low anterior resection, abdominoperineal resection, left colon resection, and transverse colon resection. The addition of each laparoscopic skill increased the complexity during each procedure. All three skills were not required for every procedure. CONCLUSIONS: Since all procedures do not require all three skills, skills can be learned sequentially if patients are chosen judiciously. A sequence of laparoscopic procedures performed by surgeons is recommended. The relative complexities for each procedure suggest an outline (map) for surgeons to use during laparoscopic colon surgery.

Abdomen↗
PubMed1994

Alteration in vascular reactivity in isolated aortic rings from portal vein-constricted rats.

It has been suggested that increased production of nitric oxide by an inducible nitric oxide synthase isoenzyme is important in the pathogenesis of the vascular abnormalities seen in human beings and animals with portal hypertension. We investigated this hypothesis by studying the in vitro vascular reactivity of isolated aortic rings from portal vein-constricted and sham-operated rats. Aortic rings from portal vein-constricted rats exhibited significantly impaired contractility to phenylephrine and potassium chloride compared with control rats. Preincubation with the nitric oxide synthase inhibitor nitro-L-arginine methyl ester significantly increased contractility to phenylephrine and potassium chloride in both portal-hypertensive and control tissues, with greater effect in the portal-hypertensive rings. Despite nitro-L-arginine methyl ester, maximal contractions were still significantly smaller in the portal-hypertensive tissues. Vascular relaxation evoked by acetylcholine, but not by the endothelium-independent vasodilator glyceryl trinitrate, was significantly impaired in the portal-hypertensive group. Our results demonstrate significant impairment in vascular function in aortic rings in this model of portal hypertension. The addition of a nitric oxide synthase inhibitor partly corrected these changes, suggesting that although nitric oxide is likely an important mediator, other factors may also be involved in the pathogenesis of these alterations in vascular function.

Acetylcholine↗
PubMed1994

Molecular analysis of the aspartate kinase-homoserine dehydrogenase gene from Arabidopsis thaliana.

The gene encoding Arabidopsis thaliana aspartate kinase (ATP:L-aspartate 4-phosphotransferase, EC 2.7.2.4) was isolated from genomic DNA libraries using the carrot ak-hsdh gene as the hybridizing probe. Two genomic libraries from different A. thaliana races were screened independently with the ak probe and the hsdh probe. Nucleotide sequences of the A. thaliana overlapping clones were determined and encompassed 2 kb upstream of the coding region and 300 bp downstream. The corresponding cDNA was isolated from a cDNA library made from poly(A)(+)-mRNA extracted from cell suspension cultures. Sequence comparison between the Arabidopsis gene product and an AK-HSDH bifunctional enzyme from carrot and from the Escherichia coli thrA and metL genes shows 80%, 37.5% and 31.4% amino acid sequence identity, respectively. The A. thaliana ak-hsdh gene is proposed to be the plant thrA homologue coding for the AK isozyme feedback inhibited by threonine. The gene is present in A. thaliana in single copy and functional as evidenced by hybridization analyses. The apoprotein-coding region is interrupted by 15 introns ranging from 78 to 134 bp. An upstream chloroplast-targeting sequence with low sequence similarity with the carrot transit peptide was identified. A signal sequence is proposed starting from a functional ATG initiation codon to the first exon of the apoprotein. Two additional introns were identified: one in the 5' non-coding leader sequence and the other in the putative chloroplast targeting sequence. 5' sequence analysis revealed the presence of several possible promoter elements as well as conserved regulatory motifs. Among these, an Opaque2 and a yeast GCN4-like recognition element might be relevant for such a gene coding for an enzyme limiting the carbon-flux entry to the biosynthesis of several essential amino acids. 3' sequence analysis showed the occurrence of two polyadenylation signals upstream of the polyadenylation site. This work is the first report of the molecular cloning of a plant ak-hsdh genomic sequence. It describes a promoter element that may bring new insights to the regulation of the biosynthesis of the aspartate family of amino acids.

Amino Acid Sequence↗
PubMed1994

Isolation of a poplar and an Arabidopsis thaliana dihydrodipicolinate synthase cDNA clone.

A poplar DHDPS cDNA clone has been isolated by functional rescue of the dapA-deficient AT997 mutant of Escherichia coli. By sequence comparison between the poplar and maize DHDPS cDNAs, two oligonucleotides were designed to perform polymerase chain reaction (PCR) on Arabidopsis thaliana genomic DNA. The PCR fragment was subsequently used to isolate an Arabidopsis DHDPS genomic and cDNA clone.

Amino Acid Sequence↗
PubMed1994

Laparoscopic-assisted sigmoid colectomy and low anterior resection.

Laparoscopic-assisted sigmoid colectomy or low anterior resection was undertaken in 30 selected patients. The median age was 51 (range, 30-85) years. Eight patients had previous abdominal surgery: four hysterectomies, two appendectomies, and two cholecystectomies. There was no mortality. Complications occurred in three patients. One patient developed a wound infection, there was one iliac artery injury, and one postoperative bleed, which did not require transfusion. Eighteen patients were operated on for primary cancer of the colon and 12 patients for benign disease. Technical aspects are described in detail. The average hospital stay was four days with most patients receiving oral analgesics by the second postoperative day. Laparoscopic colon resection can be an alternative to open surgery.

Colectomy↗
PubMed1994

Altered prostacyclin synthesis by aortae from hepatic portal vein-constricted rats: evidence for effects on protein kinase C and calcium.

To investigate the mechanisms causing reduced systemic vascular reactivity to vasoconstrictor agents in portal hypertension, we studied receptor- and signal-transduction-linked PGI2 (a vasodilator) synthesis (measured as 6-oxo-PGF1 alpha by radioimmunoassay) in the aorta (ex vivo) of portal vein-constricted rats. PGI2 synthesis was stimulated by adrenaline (via heterogeneous alpha-adrenoceptors), phorbol ester dibutyrate (a protein kinase C activator), arachidonic acid (the substrate for PGI2 synthesis) and the Ca2+ ionophore A23187 (A23187) and thapsigargin (both of which elevate intracellular Ca2+, which in turn elicits the release of arachidonic acid). The release of PGI2 by the aortae of rats with portal hypertension in comparison to sham-operated controls was: 1) enhanced in response to adrenaline, 2) reduced in response to phorbol ester dibutyrate, A23187 and thapsigargin and 3) unchanged in response to arichidonic acid. These data indicate that in aortae from rats with experimental portal hypertension: i) there are no changes in the enzymes involved in PGI2 synthesis (cyclooxygenase, PGI2 synthase), ii) there is a specific increase in adrenoceptor-linked PGI2 synthesis in aortae which may contribute to arterial vasodilation in this experimental model and 3) the diminished response of PGI2 synthesis to A23187, phorbol ester dibutyrate and thapsigargin indicates that there is a generalised attenuation of protein kinase C activator activity and of Ca2+. Since Ca2+ is a key component of excitation-contraction coupling and protein kinase C activator has been implicated in mediating this event, attenuation of these systems may also explain, at least in part, the known reduced vasoactivity of aortae from rats with portal hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Differential interactions of promoter elements in stress responses of the Arabidopsis Adh gene.

The Adh (alcohol dehydrogenase, EC 1.1.1.1.) gene from Arabidopsis thaliana (L.) Heynh. can be induced by dehydration and cold, as well as by hypoxia. A 1-kb promoter fragment (CADH: -964 to +53) is sufficient to confer the stress induction and tissue-specific developmental expression characteristics of the Adh gene to a beta-glucuronidase reporter gene. Deletion mapping of the 5' end and site-specific mutagenesis identified four regions of the promoter essential for expression under the three stress conditions. Some sequence elements are important for response to all three stress treatments, whereas others are stress specific. The most critical region essential for expression of the Arabidopsis Adh promoter under all three environmental stresses (region IV: -172 to -141) contains sequences homologous to the GT motif (-160 to -152) and the GC motif (-147 to -144) of the maize Adh1 anaerobic responsive element. Region III (-235 to -172) contains two regions shown by R.J. Ferl and B.H. Laughner ([1989] Plant Mol Biol 12: 357-366) to bind regulatory proteins; mutation of the G-box-1 region (5'-CCACGTGG-3', -216 to -209) does not affect expression under uninduced or hypoxic conditions, but significantly reduces induction by cold stress and, to a lesser extent, by dehydration stress. Mutation of the other G-box-like sequence (G-box-2: 5'-CCAAGTGG-3', -193 to -182) does not change hypoxic response and affects cold and dehydration stress only slightly. G-box-2 mutations also promote high levels of expression under uninduced conditions. Deletion of region I (-964 to -510) results in increased expression under uninduced and all stress conditions, suggesting that this region contains a repressor binding site. Region II (-510 to -384) contains a positive regulatory element and is necessary for high expression levels under all treatments.

Alcohol Dehydrogenase↗
PubMed1994

Response of recurrent brain metastases in malignant melanoma to 5-fluorouracil and interferon-alpha therapy.

A 36-year-old woman underwent removal of a stage II malignant melanoma from the left ankle in 1985. A single brain metastasis to the right frontal lobe was removed in July 1986. Postoperatively, she received 5-fluorouracil, cisplatin, and etoposide (VP-16) in conjunction with radiation therapy. She achieved remission until March 1988, when left hemiparesis occurred suddenly. Computed tomography and magnetic resonance scans revealed multiple brain metastases. She was treated with a combination of 5-fluorouracil, 1,000 mg/m2 in a 24-hour continuous IV infusion for 5 days; interferon-alpha, 10 million units in subcutaneous injection daily for 10 days; and oral cimetidine, 1,200 mg daily for 7 days. This regimen, repeated every 4 to 6 weeks for four cycles, was well tolerated, with complete remission of neurological deficits and resolution of the lesions seen on the brain scans until she died 11 months later of intracranial hemorrhage secondary to severe thrombocytopenia.

Adult↗
PubMed1994

An electrophysiological study on children and young adults with Alport's syndrome.

Alport's syndrome is characterised by progressive haematuric nephritis and high tone sensorineural hearing loss. Ocular signs are variable, the most consistent findings being anterior lenticonus and retinal flecks in the macula and mid peripheral areas. Previous electrophysiological studies on patients with Alport's syndrome have mostly been on adult patients undergoing haemodialysis, or after renal transplantation. A group of young patients with Alport's syndrome were studied to assess if early electrophysiological changes were detectable. A total of 20 patients (15 males and five females) between the ages of 3.5 and 22 years (mean 12.7 (years) were examined and compared with control subjects. Visual evoked potentials and electroretinograms were obtained following flash and pattern reversal stimulation. Electro-oculograms were also recorded. No significant electrophysiological changes were found in any of the 20 patients, including four who had visible fundus changes.

Adolescent↗
PubMed1994

Chemoradiotherapy for the treatment of regionally advanced head and neck cancers.

Despite the use of aggressive surgery and radiotherapy, patients with locoregionally advanced squamous cell carcinoma of the head and neck continue to suffer poor local control and poor survival. Chemotherapy produces excellent regressions of locoregional disease when given as part of initial induction therapy. The use of chemoradiotherapy for regionally advanced disease offers the possibility of organ preservation and retention of organ function for many of these patients. Randomized studies have suggested that chemoradiotherapy also offers better local control and survival than radiotherapy alone. Many chemotherapy regimens used in modern chemoradiotherapy include cisplatin. Because of its ease of outpatient administration, lesser degree of nausea and vomiting, reduced nephrotoxicity, improved nutritional status during therapy, and predictable myelotoxicity, carboplatin has important advantages over cisplatin. Carboplatin possesses well-defined single-agent activity against head and neck cancers, and produces excellent responses in combination with 5-fluorouracil in previously untreated patients. Sequential studies at the University of Maryland Cancer Center showed that weekly carboplatin could be safely and easily combined with standard doses and fractions of radiotherapy. With this regimen, 57% of the patients achieved a complete response and 21% achieved a partial response. Although the addition of bleomycin to this regimen proved somewhat toxic, concurrent carboplatin and radiotherapy allows for the further testing of new agents in developing a combination chemotherapy/concurrent radiotherapy program. Such regimens may improve local control and survival, and may be developed further for organ preservation studies.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Maintenance therapy for obstructive lung disease. How to achieve the best response with the fewest agents.

Asthma is now thought to be primarily an inflammatory condition with secondary bronchospasm; hence, the mainstay of maintenance therapy is an inhaled anti-inflammatory drug, either a corticosteroid (especially in adults) or a mast-cell stabilizer (especially in children). Inhaled beta agonists are reserved for acute exacerbations and systemic corticosteroids for severe refractory disease. Oral theophylline is sometimes helpful, especially for nocturnal exacerbations. Chronic bronchitis and emphysema almost always stem from cigarette smoking. Bronchospasm is the predominant cause of symptoms, and maintenance therapy with an inhaled anticholinergic (eg, ipratropium bromide [Atrovent]) is the best approach. If symptoms are not controlled, an inhaled bronchodilator should be added. An oral or inhaled corticosteroid benefits a minority of patients. Theophylline is especially helpful for chronic bronchitis and nocturnal exacerbations.

Administration, Inhalation↗
PubMed1993

Probucol and other antioxidants prevent the inhibition of endothelium-dependent relaxation by low density lipoproteins.

Hypercholesterolaemia and atherosclerosis impair responses to endothelium-derived nitric oxide (EDRF) in human and animal coronary arteries, a dysfunction that correlates with elevated low density lipoproteins (LDL). Previous studies show that native LDL immediately and reversibly inhibit acetylcholine-evoked EDRF responses in rabbit aortic ring precontracted with noradrenaline or serotonin whereas Cu(2+)-oxidised LDL (oxLDL) inhibit relaxations after 30 min with a potency that varies with the donor. We now show that antioxidants, probucol (10 microM) and ascorbic acid (100 microM) in vitro, prevent the inhibition by native LDL, indicating that this effect involves free radicals. As expected, the antioxidants had no influence on the inhibition by oxLDL. Superoxide dismutase appeared to have no effect on the inhibition by native or oxLDL. The oral administration of probucol to selected volunteers also prevented the inhibition of relaxation by their native LDL. These preparations showed a diminished susceptibility to oxidation and their oxLDL caused a markedly reduced and always reversible inhibition of relaxation compared to the potent and sometimes irreversible inhibition prior to administration of the drug. We conclude that antioxidants such as probucol reduce the formation of free radicals and the oxidative modification of LDL that lead to the impairment of EDRF responses and may prevent this same dysfunction in hypercholesterolaemia and atherosclerosis.

Acetylcholine↗
PubMed1993

College students' perception of vulnerability/susceptibility and desire for health information.

The specific aims of this study were to develop a questionnaire and conduct a survey of college students 18-22 years of age, in order to determine (1) their perception of being vulnerable and susceptible to health problems and (2) their interest in receiving help and information about health maintenance. Material from four 2-h focus groups provided the content for the initial questionnaire. Pilot testing of the early drafts consisted of several phases in which students completed the tool in both group situations and in face-to-face interviews. The final questionnaire was completed by 364 students on two campuses in the Midwest. Two scales were identified using factor analysis and analysis for internal consistency. The Vulnerability/Susceptibility Scale demonstrated a good reliability (Kuder-Richardson-20 = 0.8136) and five factors were identified through factor analysis. The Information Scale demonstrated a high reliability (Kuder-Richardson-20 = 0.8958) and two factors were identified through factor analysis. Based on analysis of variance (ANOVA) data, a model was developed using the variables of the Vulnerability/Susceptibility Scale, the Information Scale, gender and health rating. The model was then tested using multiple regression analysis. This study identified health related areas about which the students feel vulnerable/susceptible and are interested in receiving health help/information. This study suggests which population of college students might be most receptive to health information and future behavioral strategies.

Adolescent↗
PubMed1993

Effect of hypothermic storage in liver allograft preservation solutions on vasoactivity and prostacyclin synthesis by the rabbit aorta, in vitro.

Primary graft dysfunction following orthoptic liver transplantation has been ascribed to thrombotic and ischemic complications in a high proportion of cases. It has been suggested that hypothermic storage of livers in preservation solutions elicits damage to the vascular endothelium. Since the endothelium controls vasoactivity and hemostasis via release of endothelium derived relaxing factor (EDRF) and prostacyclin (PGI2), storage injury to the endothelium may predispose the allograft to thrombosis, ischemia and impaired perfusion. In order to test this, the effect of long-term hypothermic storage in modified University of Wisconsin solution (UW), kidney perfusion solution (KPS) and minimum essential medium (MEM) on phenylephrine (PE)-stimulated contraction and acetylcholine (ACh)-stimulated relaxation, as well as PGI2 release by rabbit aortic rings was investigated. Following cold storage for 24, 48 and 72 h, PE and ACh dose response curves were unaffected by storage in MEM, UW or KPS. Following hypothermic storage for 24 h and 48 h, PGI2 release (stimulated with PE, ACh, arachidonate, fluoride, calcium ionophore and phorbol ester) was not significantly altered from zero time responses. These results demonstrate that hypothermic storage of rabbit aortic rings in both UW and KPS do not influence two key endothelial functions (the release of EDRF or PGI2) which in turn indicates that endothelial damage associated with reperfusion following hypothermic storage is not causally related to alterations in EDRF and PGI2 release.

Animals↗
PubMed1993

Bacillus subtilis PrsA is required in vivo as an extracytoplasmic chaperone for secretion of active enzymes synthesized either with or without pro-sequences.

In prsA (protein secretion) mutants of Bacillus subtilis, decreased levels of exoproteins, including alpha-amylase and subtilisins, are found extracellularly. The effect of prsA on subtilisin secretion is elaborated here. Extracytoplasmic folding and secretion of active subtilisin is assisted by the N-terminal pro-sequence of its precursor. In this paper we present evidence that the product of the prsA gene is additionally required for these processes in vivo. We examined inducible expression of different subtilisin-alkaline phosphatase fusion genes in the prsA3 mutant. We found massive degradation of the fusion proteins, and a lack of enzymatic activity in the protein secreted. We suggest that PrsA is a novel chaperone with a predicted extracytoplasmic location, and is important in vivo for the proper conformation of various exoproteins, including those with pro-sequence (like subtilisin) and those without (like alpha-amylase).

Alkaline Phosphatase↗
PubMed1993

Eye movement and electrophysiological findings in an infant with hemispheric pathology.

A visually unresponsive infant had a normal ophthalmological examination. Eye-movement studies using electro-oculography revealed asymmetrical binocular smooth pursuit, binocular optokinetic nystagmus and vestibulo-ocular reflex. Electrophysiological testing showed markedly asymmetrical occipital flash and pattern visual evoked potentials. Both investigations suggested a posterior right-hemispheric problem, which was confirmed with cranial ultrasound. This case study illustrates the usefulness of non-invasive techniques in neuro-ophthalmological investigations of young children.

Brain Diseases↗