Construction of matched verbal and design continuous paired associate tests.

We developed verbal and figural continuous paired associate tests (CPAT) that are matched on internal consistency and on the distributional properties of mean item difficulty, variance, and skewness. The Verbal CPAT is composed of high frequency nouns, verbs, and adjectives. Selection of the designs was guided by literature on the effects of right-hemisphere damage on memory for designs. One hundred subjects were given 80 items from the verbal CPAT and 80 items from the designs CPAT. Twenty subjects at these five ranges of Wechsler Memory Quotient were evaluated: less than or equal to 79, 80-89, 90-99, 100-109, greater than or equal to 109. The final 40-item version of the Verbal CPAT had a mean of 26.72, a SD of 7.03, and an alpha of .859. The Designs CPAT had a mean of 26.42, a SD of 7.75, and an alpha of .886. Neither test was significantly skewed. These matched tests should be useful in making inferences about differences between verbal and figural memory that are not confounded with the problem of differential test sensitivity.

Transverse colon volvulus: case reports and review.

Volvulus of the transverse colon is an uncommon event but results in mortality or significant morbidity relatively more often than cecal or sigmoid volvulus. Two cases are presented with emphasis on incidence, predisposing factors, clinical presentation, and radiologic examination. The need for early diagnosis and surgical intervention is stressed.

Retention cysts of Cowper's duct.

Retention cysts arising from obstructed Cowper's ducts are rare lesions of the anterior urethra. Five cases are reported, 3 in male infacts and 2 in young boys. In children and adults the cysts may cause dysuria, urinary frequency, or urinary retention. The etiology of Cowper's duct cysts remains uncertain, but both congenital and acquired cysts have been described. The radiographic findings are characteristic: a smooth, rounded filling defect is seen on the ventral wall of the proximal bulbous urethra during voiding cystourethrography. After fulguration of the cyst, urethrography may reveal reflux into a dilated Cowper's duct.

Function of ubiquinone in Escherichia coli: a mutant strain forming a low level of ubiquinone.

A ubiquinone-deficient mutant of Escherichia coli K-12 forming 20% of the normal amount of ubiquinone was compared with a normal strain. This lowered concentration of ubiquinone is still four times the concentration of cytochrome b(1). The mutant strain grew more slowly than the normal strain on a minimal medium with glucose as sole source of carbon and gave a lower aerobic growth yield than the normal strain. The reduced nicotinamide adenine dinucleotide (NADH) oxidase rate in membranes from the mutant strain was 40% of the oxidase rate in membranes from the normal strain, and the percentage reduction of cytochrome b(1) in the aerobic steady state, with NADH as substrate, was increased in membranes from the mutant strain. It is concluded that ubiquinone is required for maximum oxidase activity at the relatively high concentration (27 times that of cytochrome b(1)) found in normal cells. The results are discussed in relation to a scheme previously advanced for ubiquinone function in E. coli.

The energy-linked transhydrogenase reaction in respiratory mutants of Escherichia coli K12.

1. Energy-linked and non-energy-linked transhydrogenase activities were assayed in membrane preparations from normal Escherichia coli K 12 and from various mutant strains. 2. The energy-linked transhydrogenase, which uses ATP as energy source, was dependent for activity on the presence of a functional Mg(2+)+Ca(2+)-stimulated adenosine triphosphatase. 3. Neither of the quinones formed by E. coli, namely ubiquinone-8 and menaquinone-8, was required for normal ATP-dependent energy-linked transhydrogenase activity. 4. The energy-linked transhydrogenase was inhibited by piericidin A at a site unrelated to the sites of inhibition of the electron-transport chain by piericidin A.

Mutations affecting iron transport in Escherichia coli.

A mutant of Escherichia coli K-12 unable to form an essential component of the enterochelin-dependent iron transport system has been isolated. This strain carries a mutation in a gene designated fep, mapping close to two genes, entA and entD, concerned with enterochelin synthesis. Strain AN102, which carries the fep(-) allele, accumulates large quantities of enterochelin and gives a growth response to sodium citrate. The cytochrome b(1) and total iron content, and the measurement of the uptake of (55)Fe(3+), indicate an impairment of the enterochelin-dependent iron transport system. The growth response to sodium citrate is related to the presence, in strain AN102, of an inducible citrate-dependent iron transport system.

The function of ubiquinone in Escherichia coli.

1. The function of ubiquinone in Escherichia coli was studied by using whole cells and membrane preparations of normal E. coli and of a mutant lacking ubiquinone. 2. The mutant lacking ubiquinone, strain AN59 (Ubi(-)), when grown under aerobic conditions, gave an anaerobic type of growth yield and produced large quantities of lactic acid, indicating that ubiquinone plays a vital role in electron transport. 3. NADH and lactate oxidase activities in membranes from strain AN59 (Ubi(-)) were greatly impaired and activity was restored by the addition of ubiquinone (Q-1). 4. Comparison of the percentage reduction of flavin, cytochrome b(1) and cytochrome a(2) in the aerobic steady state in membranes from the normal strain (AN62) and strain AN59 (Ubi(-)) and the effect of respiratory inhibitors on these percentages in membranes from strain AN62 suggest that ubiquinone functions at more than one site in the electron-transport chain. 5. Membranes from strain AN62, in the absence of substrate, showed an electron-spin-resonance signal attributed to ubisemiquinone. The amount of reduced ubiquinone (50%) found after rapid solvent extraction is consistent with the existence of ubiquinone in membranes as a stabilized ubisemiquinone. 6. The effects of piericidin A on membranes from strain AN62 suggest that this inhibitor acts at the ubiquinone sites: thus inhibition of electron transport is reversed by ubiquinone (Q-1); the aerobic steady-state oxidation-reduction levels of flavins and cytochrome b(1) in the presence of the inhibitor are raised to values approximating those found in the membranes of strain AN59 (Ubi(-)); the inhibitor rapidly eliminates the electron-spin-resonance signal attributed to ubisemiquinone and allows slow oxidation of endogenous ubiquinol in the absence of substrate and prevents reduction of ubiquinone in the presence of substrate. It is concluded that piericidin A separates ubiquinone from the remainder of the electron-transport chain. 7. A scheme is proposed in which ubisemiquinone, complexed to an electron carrier, functions in at least two positions in the electron-transport sequence.

Studies on ferrochelatase. The effects of thiols and other factors on the determination of activity.

1. Haems are unstable under aerobic conditions in the presence of thiols, which are used to activate the ferrochelatase enzyme; catalase inhibits this degradation of haem. In addition, thiols interfere with the determination of protohaem as its pyridine haemochromogen derivative. 2. Three ferrochelatase assays are described that minimize interference by these two reactions. Two of these assays involve measurement of porphyrin utilization, one spectrophotometrically and the second spectrofluorimetrically. The third assay measures haem formation by a pyridine haemochromogen technique. Results obtained with these three methods were in close agreement at a GSH concentration of 4mm. 3. The stimulatory effect of GSH on ferrochelatase has been confirmed. The spectrum of the haem formed is dependent on GSH concentration; at high GSH concentrations (20mm) the haem is in the reduced state, but at low concentration (4mm) the spectrum of the product resembles that of an oxidized haemoprotein such as ferrihaemoglobin. 4. The inhibitory effect of oxygen on ferrochelatase activity has been confirmed by spectrophotometric assay of porphyrin disappearance.