Biomedical subjects

J M Becker

Publications and source records attributed to J M Becker.

At least 163 records · Page 9Linked to original sources

PubMed1987

Chemochromatography: its use for the separation of nikkomycins X and Z.

A novel mode of reversed-phase high-performance liquid chromatography in which the mobile phase reacts chemically with the compounds to be separated was developed. Nikkomycin X and nikkomycin Z, two natural isomeric nucleoside peptide antibiotics, move as a single peak on a C18 reversed-phase column using an aqueous trifluoroacetic acid mobile phase. Addition of sodium bisulfite (1.0%) to the mobile phase results in the formation of a polar bisulfite addition product with nikkomycin X, but not with nikkomycin Z, inside the HPLC column. This type of reactive chromatography, or chemochromatography, led to the analytical and preparative separation of nikkomycins X and Z which are normally very intractable to separation by conventional chromatographic techniques.

Aminoglycosides↗

PubMed1987

Regulation of dipeptide transport in Saccharomyces cerevisiae by micromolar amino acid concentrations.

Prototrophic Saccharomyces cerevisiae X2180, when grown on unsupplemented minimal medium, displayed little sensitivity to ethionine- and m-fluorophenylalanine-containing toxic dipeptides. We examined the influence of the 20 naturally occurring amino acids on sensitivity to toxic dipeptides. A number of these amino acids, at concentrations as low as 1 microM (leucine and tryptophan), produced large increases in sensitivity to leucyl-ethionine, alanyl-ethionine, and leucyl-m-fluorophenylalanine. Sensitivity to ethionine and m-fluorophenylalanine remained high under either set of conditions. The addition of 0.15 mM tryptophan to a growing culture resulted in the induction of dipeptide transport, as indicated by a 25-fold increase in the initial rate of L-leucyl-L-[3H]leucine accumulation. This increase, which was prevented by the addition of cycloheximide, began within 30 min and peaked approximately 240 min after a shift to medium containing tryptophan. Comparable increases in peptidase activity were not apparent in crude cell extracts from tryptophan-induced cultures. We concluded that S. cerevisiae possesses a specific mechanism for the induction of dipeptide transport that can respond to very low concentrations of amino acids.

Amino Acids↗

PubMed1987

The activation of adenylate cyclase by guanyl nucleotides in Saccharomyces cerevisiae is controlled by the CDC25 start gene product.

In the thermosensitive cdc25 start mutant of Saccharomyces cerevisiae, the regulation of adenylate cyclase by guanyl nucleotides was rapidly nullified when the enzyme was prepared from nonsynchronized cells shifted to the restrictive temperature. In agreement with previous in vivo complementation studies, this biochemical defect was fully suppressed by the expression of either the whole cloned CDC25 gene or its C-terminal portion. Moreover, membranes prepared from cdc25(Ts) cells grown at the permissive temperature evinced an altered regulation of adenylate cyclase by guanyl nucleotides. These results indicate that the CDC25 protein, together with RAS, is involved in the regulation of adenylate cyclase by guanyl nucleotides and raise the possibility that adenylate cyclase might form a ternary complex with RAS and CDC25.

Adenylyl Cyclases↗

PubMed1987

Towards determination of the structure of the Saccharomyces cerevisiae a-factor: an acylated pentadecapeptide blocks a-factor activity.

Putative a-factor peptides YIIKGVFWADP, YIIKGVFWANP, YIIKGLFWADP, YIIKGLFWANP, YIIKGVFWDPA, and YIIKGVFWDPACVIA and several peptide derivatives were synthesized and were found to be inactive in growth arrest assays, yet they blocked the activity of biological a-factor. Antagonism was greatest with YIIKGVFWDPAC(palmitoyl)VIA. Thus, the structure of a-factor may be a lipopeptide resembling this palmitoylated pentadecapeptide.

Acylation↗

PubMed1986

Canine mucosal antrectomy.

Our primary aim was to determine whether mucosal antrectomy decreases postcibal serum gastrin and gastric acid secretion. In four dogs with proximal gastric vagotomy and a Heidenhain pouch, mucosal antrectomy decreased the integrated postcibal serum gastrin response from a mean +/- SEM of 2.0 +/- 0.2 ng X h/mL before antrectomy to 0.8 +/- 0.1 ng X h/mL after antrectomy, while it decreased postcibal output of hydrochloric acid from the pouch from 9.5 +/- 3.3 mEq/7 h (9.5 +/- 3.3 mmol/7 h) to 4.3 +/- 2.2 mEq/7 h (4.3 +/- 2.2 mmol/7 h). However, these decreases were temporary in two of the four dogs. In five additional dogs without vagotomy, the distal, antral, mucosal gastrin level increased from 1 +/- 1 micrograms/g of tissue before mucosal antrectomy to 5 +/- 1 micrograms/g of tissue after the antrectomy. Moreover, gastrin and G cells were present in corporal mucosa transferred to the antrum in three of five dogs after the antrectomy, where none had been present in the corporal mucosa before the antrectomy. The conclusion was that mucosal antrectomy decreased serum gastrin and hydrochloric acid output from the stomach, but that these changes were counteracted in part by hyperplasia of residual G cells and G-cell neogenesis after the operation.

Animals↗

PubMed1986

A technique for safe transanal passage of the circular end-to-end stapler for low anterior anastomosis of the colon.

Two techniques are currently available for the creation of low anterior rectal stapled anastomoses. The first technique requires the placement of a pursestring suture at the superior margin of the rectal cuff, which is technically difficult. In the second technique, the rectal cuff is closed with a linear stapler. The circular end-to-end stapler, with the anvil removed, is then passed through an enterotomy in the rectal remnant. We describe an easy and safe method that obviates difficulties during the transanal passage of the stapler and minimizes the risk of injury to the rectum. This method uses an inexpensive and readily available rubber catheter and metal guide.

Catheterization↗

PubMed1986

Yeast alpha-factor and somatostatin enhance binding of [3H]estradiol to proteins in rat pancreas and Saccharomyces cerevisiae.

Pancreatic tissue contains an [3H]estradiol-binding protein that requires a coligand in the steroid-binding reaction. The endogenous coligand appears to be the tetradecapeptide somatostatin. Yeast alpha-factor, a tridecapeptide pheromone that induces conjugation between haploid cells of opposite mating type, was found to be as effective as somatostatin in enhancing specific binding of [3H]estradiol to partially purified pancreatic protein. Supernatant fractions from yeast cells also contain an [3H]estradiol-binding protein. alpha-Factor can enhance specific binding of [3H]estradiol to such yeast fractions. Somatostatin, somatostatin analogues, and an analogue of alpha-factor enhanced binding of [3H]estradiol but did not inhibit cell growth or induce morphological changes in S. cerevisiae. Thus, it appears that coligand-requiring [3H]estradiol-binding activity and mating in yeast are not directly related.

Amino Acid Sequence↗

PubMed1986

Colonic mucosal dissection following electrocautery or laser polypectomy.

Mucosal proctectomy and ileoanal anastomosis is being increasingly performed on patients with familial polyposis, many of whom have undergone previous subtotal colectomy followed by endoscopic surveillance and polypectomy with monopolar electrocautery (MPEC) or, more recently, argon laser (AL). Our aim was to compare the ease of mucosal dissection following polypectomy with MPEC or AL in the canine colon. At celiotomy, two groups of fifteen 5- to 7-mm sessile polyps were surgically created in the descending colon of five mongrel dogs. Six weeks later, each animal underwent flexible colonoscopy and polyp fulguration with MPEC (15 polyps) and AL (15 polyps). Fulguration was performed weekly for 2-3 weeks until all polyps had been obliterated. Ten weeks later, mucosal dissection was performed with the operating team unaware of prior treatment. Mucosal dissection was scored for dissectability (1 to 4; 1 = facile, 4 = difficult), blood loss, operating time, and number of mucosal perforations with the last three parameters normalized to 100 cm2 of mucosa. AL and MPEC were equally effective at polyp obliteration; however, more AL-treated polyps required retreatment than MPEC-treated polyps (P less than 0.05). After AL treatment, mucosal dissection was more facile [dissectability index (mean +/- SEM): 1.4 +/- 0.2 vs 2.6 +/- 0.2; P less than 0.05] and could be performed more quickly (15.1 +/- 2.4 min vs 23.6 +/- 2.7 min; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Idiopathic infant pyoceles.

Three infants presented with acute scrotal swelling, erythema, and a tender irreducible firm mass within the scrotum. All patients were operated upon with the preoperative diagnosis of testicular torsion. At operation, grossly purulent fluid was found in a hydrocele sac. In all the cases, the testes were normal and no source of the scrotal infection was identified. A variety of bacterial organisms were cultured and responded readily to antibiotics. Follow-up has documented survival of the testes without apparent atrophy. "Idiopathic" infant pyocele is rarely described and consequently, not included in the differential diagnosis of patients with acute surgical conditions of the inguinoscrotal region.

Diagnosis, Differential↗

PubMed1986

Synthesis and biological properties of chitin synthetase inhibitors resistant to cellular peptidases.

The synthesis and biological properties of seven polyoxins (4-10) designed to avoid peptidase hydrolysis in Candida albicans are presented. Five dipeptidyl and two tripeptidyl polyoxin analogues were synthesized by coupling an amino acid active ester or azlactone to uracil polyoxin C (2) or polyoxin D (1), subsequent removal of the protecting group, and purification by preparative HPLC. A new and novel route for introducing an n-propyl group onto the alpha-amino group of peptides is reported. With the exception of a carboxamide derivative, 8, all analogues were resistant to hydrolysis by a cell extract or permeabilized cells of Candida. Chitin synthetase inhibition constants were determined for 4-10 and the KI values ranged from 7.15 X 10(-6) M for octanoyl-phenylalanyl-polyoxin D (10) to 1.06 X 10(-3) M for D-tryptophanyl-uracil polyoxin C (6). These novel polyoxins do not compete with the transport of either peptides or uridine into the cell. Millimolar concentrations of compounds 4-10 are required to inhibit growth, cause morphological alterations, or reduce the viability of C. albicans.

Antifungal Agents↗

PubMed1986

Controlled open lesser sac drainage for pancreatic abscess.

Recent studies suggest that morbidity and mortality in patients with pancreatic abscess can be lessened if controlled open lesser sac drainage (COLD) is performed rather than traditional closed drainage (CD). To determine whether the outcome of patients treated by COLD was more favorable, 81 consecutive patients with pancreatic abscess managed surgically between 1966 and 1985 were studied. COLD, consisting of initial wide debridement of the abscess cavity, open packing, suction drainage, repeated operative pack changes, and lavage was used in 17 patients and CD in 64 patients. Age, sex, etiology of pancreatitis, and radiographic and laboratory findings were similar between treatment groups. However, the number of patients with overt systemic sepsis and those at increased risk of death based on Ranson signs associated with the predisposing episode of pancreatitis were greater in the COLD group than in the CD group (100% vs. 61%, and 92% vs. 44%, respectively; p less than or equal to 0.05 for both). Overall mortality in COLD and CD patients was 18% and 44%, respectively (p less than 0.05). However, in patients at increased risk of death (positive Ranson signs greater than or equal to 3), mortality after COLD and CD was 18% and 70%, respectively (p less than 0.05). Controlled open drainage may be the treatment of choice in patients with pancreatic abscess precipitated by severe pancreatitis (Ranson signs greater than or equal to 3) and associated with overt systemic sepsis.

Abscess↗

PubMed1986

Ileal pouch-anal anastomosis. A single surgeon's experience with 100 consecutive cases.

Between August 1982 and November 1985, 100 patients underwent ileal "J" pouch-anal anastomosis (IPAA) at the University of Utah. All operations were performed in a standard fashion by a single surgeon. Seventy-eight patients were operated on for chronic ulcerative colitis and 22 for familial polyposis coli. Sixty of the patients were male and 40 were female with a mean age of 33.2 years and a range of 11-63 years. Mean +/- SEM operating time was 5.9 +/- 0.4 hours, blood loss was 666 +/- 49 ml, and total hospitalization was 10.1 +/- 0.3 days. No operative deaths occurred. The overall operative morbidity was 13% after IPAA. Clinical "pouchitis" was observed in 18 patients, all of whom were operated on for chronic ulcerative colitis. No patients had frank incontinence. Twenty per cent of patients experienced frequent nocturnal leakage in the early postoperative period with a significant improvement over the ensuing 6 months. Stool frequency at 1, 3, 6, 12, and 24 months was 7.5 +/- 0.2, 6.5 +/- 0.1, 6.2 +/- 0.3, 5.4 +/- 0.1, and 5.4 +/- 0.2, respectively. Stool frequency at 12 months correlated inversely with ileal pouch capacity and the diagnosis of familial polyposis. It is concluded that ileal pouch-anal anastomosis is a safe and effective operation for patients with chronic ulcerative colitis and familial polyposis coli.

Adolescent↗

PubMed1986

Polyoxin D inhibits colloidal gold-wheat germ agglutinin labelling of chitin in dimorphic forms of Candida albicans.

Yeasts and mycelia of the pathogen Candida albicans grown in the presence of polyoxin D, a competitive inhibitor of chitin synthase, formed chains of swollen bulbous cells as observed by fluorescence microscopy. Wheat germ agglutinin (WGA) complexed to colloidal gold (Au) was used as a specific label at the ultrastructural level to visualize chitin in walls of control and polyoxin-treated cells. In control cells, Au-WGA labelling was preferentially localized in the innermost wall layers and was predominant at bud scars and septa. After 4.5 h in 4 mM-polyoxin D, budding in yeasts and lateral wall growth in mycelia continued, but primary septa failed to form and no Au-WGA labelling was detected in the walls. These results demonstrated that the morphological alterations caused by polyoxin D were due to the absence of chitin, a wall component important for formation of primary septa and for maintenance of structural integrity during morphogenesis.

Antifungal Agents↗

PubMed1986

Hydrophobic polyoxins are resistant to intracellular degradation in Candida albicans.

Two novel polyoxins, N-epsilon-(octanoyl)-lysyl-uracil polyoxin C (Oct-Lys-UPOC) and N-gamma-(octyl)-glutaminyluracil polyoxin C (Oct-Gln-UPOC), were synthesized by reacting uracil polyoxin C with the appropriate amino acid p-nitrophenyl ester. Oct-Lys-UPOC and Oct-Gln-UPOC were strong inhibitors (Kis = 1.7 X 10(-6)M) of chitin synthetase from Candida albicans membrane preparations. In a permeabilized-cell assay, Oct-Gln-UPOC had a 10-fold-lower inhibitory activity toward chitin synthetase than did the Oct-Lys-UPOC analog. Both compounds were resistant to hydrolysis by a cell extract of C. albicans H317; however, Oct-Gln-UPOC was hydrolyzed with a half-life of 23 min by a permeabilized-cell preparation. Oct-Lys-UPOC was resistant to hydrolysis by permeabilized cells. Oct-Gln-UPOC and Oct-Lys-UPOC did not compete with the transport of peptides or uridine into the cell. At concentrations up to 2 mM these two new polyoxins were ineffective in the inhibition of cell growth or reduction of cell viability, but they induced aberrant morphologies in C. albicans at a concentration of 0.25 mM. These data suggest that polyoxins containing hydrophobic amino acids retain strong chitin synthetase inhibitory activity and are resistant to cellular hydrolysis. They provide the first example of effective synthetic chitin synthetase inhibitors which are stable inside C. albicans.

Anti-Bacterial Agents↗

PubMed1986

Biological activity of the Asn-5,Arg-7 tridecapeptide encoded by MF alpha 2 of Saccharomyces cerevisiae.

The precursor predicted by the nucleotide sequence of the MF alpha 2 gene of Saccharomyces cerevisiae contains one copy of the tridecapeptide alpha-factor previously characterized (H2N-Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr-COOH) and one copy of a peptide that contains two conservative amino acid substitutions (H2N-Trp-His-Trp-Leu-Asn-Leu-Arg-Pro-Gly-Gln-Pro-Met-Tyr-COOH). To determine whether the novel molecule possesses biological activity, the Asn-5,Arg-7 tridecapeptide was prepared chemically by solid-phase peptide synthesis. Growth arrest and morphogenesis assays gave identical activity profiles for the Asn-5,Arg-7 peptide and the other gene product, the Gln-5,Lys-7 peptide. The activities of the two peptides were additive and indistinguishable for S. cerevisiae X2180-1A. When present in fourfold molar excess, the biologically inactive desTrp-1,Ala-3 dodecapeptide reversed activity of the Asn-5,Arg-7 and Gln-5,Lys-7 tridecapeptides. Furthermore, neither peptide caused growth arrest of a MATa ste2(Ts) mutant when assayed at the restrictive temperature. These studies suggest that both pheromones interact with the alpha-factor receptor in a similar manner.

Amino Acid Sequence↗

PubMed1986

Structure-activity relationships of the yeast alpha-factor.

The yeast Saccharomyces cerevisiae produces a peptide pheromone, termed the alpha-factor, as a prelude to sexual conjugation. Haploid MAT alpha-cells, but not haploid MAT a-cells or MAT a/alpha-diploids, produce this tridecapeptide of the structure: Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr. Structural analogues of the alpha-factor have been prepared with alterations in many of the residues, derivatized peptides have been synthesized, and truncated and elongated peptides have been studied. These peptides have been analyzed for their biological activities by various assays. Mutants of S. cerevisiae have been isolated that do not respond to alpha-factor or are supersensitive to the pheromone and its analogues. The mating system of S. cerevisiae provides a powerful model in which genetics, biochemistry, and molecular biology can be used to unravel the mysteries of peptide hormone structure and function.

Amino Acid Sequence↗

PubMed1986

Ileoanal pull-through: a new surgical alternative to ileostomy and a new challenge in diet therapy.

Colectomy mucosal proctectomy, and endorectal ileoanal pull-through is presently considered the best alternative for many patients with chronic ulcerative colitis, familial polyposis, and Gardner's syndrome. Although continence is achieved in nearly all patients who undergo the operation, high stool frequency and poor stool consistency are not infrequently encountered, particularly in the early postoperative period. Dietary control plays a likely role in postoperative management. At present, however, there are no published data to support specific dietary interventions. On the basis of our clinical experience and some preliminary study results, we have developed a comprehensive dietary regimen which is outlined in Table 1. Many questions in regard to the optimal diet for this patient population are presently unanswered, thus opening an exciting new area of nutrition research.

Anal Canal↗

PubMed1986

Changes in body composition and dietary intake after gastric partitioning for morbid obesity.

Patients who undergo gastric partitioning for morbid obesity lose weight rapidly in the first year after surgery. This study measured changes in body composition and dietary intake at 3 months, 6 months, and 1 year after gastric partitioning. Body composition was determined by total-body gamma-ray spectrometry. Records of dietary intake were computer analyzed for nutritional content with the Ohio State Nutrient Analysis Data Base. All patients lost a significant amount of weight at 3, 6, and 12 months after surgery. Loss of lean tissue comprised 25% of the total weight loss at 3 months but only 20% of the total at 1 year. Before surgery the mean energy intake was 2592 kcal and the mean protein intake was 92 gm. After 3 months, energy intake was 745 kcal and protein 32 gm. One year after surgery energy intake was 1089 kcal and protein 41 gm per day. We conclude that patients lose a significant amount of lean body tissue in the first 3 months after gastric partitioning but the loss does not continue, and 1 year after surgery some lean tissue is actually regained. This initial loss is due to a combination of a very restrictive dietary regimen and the body's metabolic response to surgery. After the first 3 months adaptation occurs and lean tissue is spared.

Adult↗