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Biomedical subjects

J H Jackson

Publications and source records attributed to J H Jackson.

At least 73 records · Page 4Linked to original sources
PubMed1982

New acetohydroxy acid synthase activity from mutational activation of a cryptic gene in Escherichia coli K-12.

A mutation in an allele identified as ilvJ662 causes the expression of acetohydroxy acid synthase activity that is resistant to feedback inhibition by L-valine. the ilvJ662 allele was transduced as an unselected marker into a strain, CU1126 (ilvB, ilvHI), deficient in acetohydroxy acid synthase activity. The ilvJ662 allele appears to code for a new acetohydroxy acid synthase activity (acetohydroxy acid synthase IV), with physical, kinetic, and physiological properties distinct from the other three isozymes. The catalytic function of acetohydroxy acid synthase IV is highly stable at 37 degrees C in the presence or absence of ethylene glycol. However, sensitivity to feedback inhibition by valine is rapidly lost at 37 degrees C, but this property is somewhat stabilized by ethylene glycol. The rate of synthesis of acetohydroxy acid synthase IV is uniquely repressed by either leucine or isoleucine. These results suggest that the ilvJ+ allele is cryptic for acetohydroxy acid synthase IV, an isozyme distinct from the other acetohydroxy acid synthases.

Acetolactate Synthase↗
PubMed1981

Three-factor reciprocal cross mapping of a gene that causes expression of feedback-resistant acetohydroxy acid synthase in Escherichia coli K-12.

The ilv-662 allele was previously identified as a mutation that caused acetohydroxy acid synthase activity to be resistant to feedback inhibition by valine (Davis et al. 1977). This allele was mapped between thr and leu by cotransduction analysis and labeled ilvJ. This report describes the mapping of ilvJ relative to genes that lie between thr and leu (ara, carA and pdxA) by three factor reciprocal cross analyses. We find that the probable gene order is thr-carA-pdxA-ilvJ-ara-leu. Although the phenotypic properties of ilvJ662 appear to be quite distinct from brnS, a gene reported to involve branched chain amino acid transport (Guardiola et al. 1974), we do not rule out possible allelism because of the uncertainty of the map position of brnS.

Acetolactate Synthase↗
PubMed1980

Neonatal and infantile candidal arthritis with or without osteomyelitis: a clinical and radiographical review of 21 cases.

Four cases of candidal arthritis and osteomyelitis are presented and 17 others are reviewed from the literature. The clinical and radiographic aspects of the entity are discussed in detail and compared with those of bacterial septic arthritis. The role of predisposing factors are elaborated. An increase in the incidence of the disease is anticipated and the diagnostic difficulties are enumerated.

Acidosis↗
PubMed1980

Diagnostic advantages of manual compression fluoroscopy in the radiologic work-up of vomiting neonates.

This paper describes a simple and effective fluoroscopic technique that remarkably improves diagnostic accuracy when evaluating vomiting newborns. The technique also minimizes the time of the examination and the radiation dose to the patient and radiology personnel. Several examples are presented illustrating the superiority of gloved hand or nonopaque compression technique to conventional contrast radiography, emphasizing babies with pyloric stenosis and midgut malrotation. The technical limitations and diagnostic pitfalls of conventional contrast modalities are compared to the highly diagnostic images obtained with manual compression fluoroscopy. All of the classic radiographic signs of pyloric stenosis can be mimicked by antral spasm or pylorospasm. Gloved hand compression overcomes antral spasm and clearly shows the true length and diameter of the pyloric canal in these two conditions. Malposition of the duodenojejunal junction is the only consistently diagnostic sign of midgut malrotation. Nonfixation of the duodenojejunal junction can be competently assessed by compression fluoroscopy, confirming malrotation and midgut volvulus simultaneously and bringing the patient to operation much sooner than with less precise conventional techniques. Gloved hand compression technique also evaluates stenotic areas in the upper gastrointestinal tract, distinguishing spasm from organic marrowing and clearly identifying those which need surgical intervention. Facilitating intubation of the duodenum is a final contribution of compression fluoroscopy.

False Negative Reactions↗
PubMed1979

Obstructive jaundice due to congenital stenosis of the ampulla of Vater.

Two infants who had obstructive jaundice due to congenital stenosis of the ampulla of Vater improved dramatically with sphincteroplasty. In one, the jaundice was complicated by hepatocellular dysfunction and mild biliary cirrhosis. Only a few cases of such an anomaly have been reported, mostly with different modes of clinical presentation.

Ampulla of Vater↗
PubMed1979

A potential pitfall of operative cholangiography in infants.

Retrograde linear extravasation of contrast media along the anatomical course of intrahepatic arborizing structures may occur during intraoperative cholangiography for evaluation of prolonged neonatal jaundice. The resultant image may mimic the appearance of intrahepatic biliary radicles.

Bile Ducts↗
PubMed1979

The radiographic signs of fatty liver.

Ninteen cases of radiographically visible fatty liver are presented. The four radiographic signs are muscle-fat interface, fat-water interface, a visible hollow viscus wall, and blurring of the medial margin of the right properitoneal fat stripe. The last sign, the authors believe, is the earliest radiographic change in developing fatty liver. In one case, isolated glycogen synthetase deficiency was the cause of fatty liver; this finding, to the authors' knowledge, has not previously been described. The value of the chest radiograph in diagnosing fatty liver is stressed.

Adolescent↗
PubMed1978

Enhanced allosteric regulation of threonine deaminase and acetohydroxy acid synthase from Escherichia coli in a permeabilized-cell assay system.

A permeabilized-cell technique for rapid assay of enzyme activity has revealed enhanced allosteric regulation of both threonine deaminase (L-threonine hydrolyase (deaminating), EC 4.2.1.16) and acethohydroxy acid synthease (acetolactate pyruvate-lyase (carboxylating), EC 4.1.3.18) in Escherichia col K-12. In the permeabilized cell assay threonine deaminase exhibited a higher Hill coefficient for inhibition by L-isoleucine, and acetohydroxy acid synthase exhibited a hypersensensitivity to allosteric inhibition by L-valine when compared to studies on crude extracts. We propose that these effects reflect the in situ microenvironments of both enzymes. Preliminary evidence further indicates that acetohydroxy acid synthase may loosely associate with the cell membrane.

Acetolactate Synthase↗
PubMed1978

Lipohemarthrosis of the elbow joint.

Radiographic demonstration of three cases of lipohemarthrosis of the elbow is discussed. Lipohemarthrosis is superior to posterior fat pad as a more specific sign of elbow trauma because posterior fat pad merely indicates increased intra-articular pressure while lipohemarthrosis is due only to intracapsular fracture or cartilage and/or ligament injury. Little fat accumulated in the anterior compartment of the joint can be demonstrated by horizontal-beam technique and lipohemarthrosis may conceivably be observed before posterior fat pad is displaced dorsally. With horizontal-beam technique, the patient is more comfortable and it seems unnecessary to irradiate the other elbow.

Child↗
PubMed1975

Mutation affecting regulation of synthesis of acetohydroxy acid synthetase in Escherichia coli K-12.

Altered regulation of synthesis of acetohydroxy acid synthetase (AHAS) was previously reported in a mutant of Escherichia coli strain K-12. The mutant strain, growing in minimal medium, exhibits a partial growth limiatation and derepression of AHAS, owing to deficient synthesis of isoleucine. The genetic lesion (ilvE503) causing the isoleucine limitation was shown to cause derepression of a valine-sensitive AHAS activity. The derepression effect of the ilvE503 mutation upon synthesis of AHAS was conclusively demonstrated by introducing both the ilvE503 allele and an altered AHAS (ilv-521) into the same cell. Evidence is presented that suggests the presence of multiple genetic regions for synthesis and control of the valine-sensitive AHAS activity.

Anti-Bacterial Agents↗
PubMed1973

Defective transamination, a mechanism for resistance to ketomycin in Escherichia coli.

A spontaneous mutant of a derivative of Escherichia coli strain K-12 resistant to 50 mug of ketomycin per ml was selected. The mutant displayed a two- to threefold derepression of the isoleucine-valine biosynthetic enzymes and a reduced growth rate in minimal medium. The lesion was found to lie in the gene (ilvE) specifying transaminase B and resulted in an isoleucine limitation. The presence of exogenous isoleucine during growth in minimal medium restored normal phenotypic properties. The reduced transaminase B activity is responsible for the resistance to ketomycin. An unusual derepression of the acetohydroxy acid synthetase in response to an isoleucine limitation was noted.

Anti-Bacterial Agents↗