Ouabain decreases apparent potassium-conductance in proximal tubules of the amphibian kidney

According to a previous study from this laboratory, the electrochemical gradient for potassium across the peritubular cell membrane of proximal tubules in the isolated perfused frog kidney increases following the application of ouabain. In order to test, if this phenomenon were due to a decrease of potassium conductance, the effects of ouabain on cell membrane resistances and the sensitivity of the peritubular cell membrane potential difference (PDpt) to step changes of peritubular potassium and bicarbonate concentration were studied. In the absence of ouabain, PDpt averaged -60 +/- 3 mV (n = 25). A step increase of peritubular potassium concentration from 3 to 18 mmol/l (pH 8.07) depolarizes PDpt (delta PDk) by +24 +/- mV (n = 8). An increase of bicarbonate from 20 to 40 mmol/l (pH 8.07) hyperpolarizes PDpt (delta PDb) by -2.8 +/- 0.4 mV (n = 9). The resistance of the luminal and peritubular cell membranes in parallel (Rm) amounts to 45 +/- 9 k omega cm (tubule length) (n = 4) and the voltage divider ratio (VDR) to 1.4 +/- 0.2 (n = 7). The resistance of the cellular cable (cellular core, Rc) approaches 131 +/- 37 M omega/cm (n = 4). Peritubular application of 0.1 mmol/l ouabain leads to a gradual decline of PDpt (t1/2 approx. 30 min), to an increase of Rm, a decrease of delta PDk and an increase of delta PDb. VDR and Rc are not changed significantly. The data point to a functional link between the sodium/potassium ATPase and the potassium conductance of the peritubular cell membrane.

Hemothorax and hemomediastinum in patients with hemophilia

Three patients with hemophilia presented with hemothoraces which resolved within 1-3 weeks following treatment with factor concentrates. Drainage of blood was not necessary. Eight previously reported cases are reviewed, and therapy and complications are summarized. We suggest that treatment of this rare complication of hemophilia with factor concentrates and avoidance of surgical intervention is indicated.

Mechanism of hydrogen ion transport in the diluting segment of frog kidney

Transepithelial H+ transport was studied in diluting segments of the isolated-perfused kidney of rana esculenta. The experiments were performed in controls as well as in K+-adapted and Na+-adapted animals (exposed to 50 mmol/l KCl or NaCl, resp. for at least 3 days). Conventional and single-barreled, liquid ion-exchanger H+-sensitive microelectrodes were applied in the tubule lumen to evaluate transepithelial H+ net flux (JHte) as well as limiting transepithelial electrical and H+ electrochemical potential differences (PDte, EHte) and luminal pH at zero net flux conditions. The measurements were made in absence (control) and presence of furosemide (5 X 10(-5) mol/l) or amiloride (10(-3) mol/l). EHte (lumen positive vs ground) was 19 +/- 3 mV in controls, 43 +/- 3 mV in K+ adapted but about zero in Na+ adapted animals. Using the corresponding PDte-values, steady state luminal pH of 7.63 +/- 0.05, 7.13 +/- 0.05 and 8.02 +/- 0.02 was calculated for the respective groups of animals (peritubular pH 7.80). In parallel, significant secretory JHte (from blood to lumen) was found in controls (14 +/- 2 pmol X cm-2 X s-1) which was stimulated by K+ adaptation (61 +/- 8 pmol X cm-2 X s-1) but reversed in direction by Na+-adaptation (-8 +/- 1 pmol X cm-2 X s-1). Amiloride inhibited secretory JHte.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of intracellular sodium activity on the transport of glucose in proximal tubule of frog kidney

Inhibition of basolateral Na+/K+ ATPase by ouabain eventually abolishes transport of glucose. The present study was performed to test, if this effect is due to a dissipation of the electrochemical gradient for sodium or due to a regulatory inhibition of sodium-coupled glucose entry across the luminal membrane at increasing intracellular sodium activity. To this end, proximal convoluted tubules of the doubly perfused isolated frog kidney were perfused alternatively with solutions containing either 5 mmol/l glucose or raffinose. The potential difference across the peritubular cell membrane (PDpt) and across the epithelium (PDte) has been recorded with conventional and across the peritubular cell membrane with ion selective microelectrodes (PDpt). In the absence of luminal glucose PDpt is (+/- SEM) -54.0 +/- 2.4 mV, PDte = -1.2 +/- 2.0 mV and PDNapt = -96 +/- 5 mV. The electrochemical gradient for sodium (mu Na+) amounts to 95 mV and intracellular sodium activity to 14 mmol/l (extracellular sodium activity is 74 mmol/l). Luminal application of glucose leads to a rapid depolarisation of PDpt (delta PDpt = 8.6 +/- 0.9 mV and PDNapt (delta PDNapt = 11.1 +/- 3.0 mV) and to hyperpolarisation of PDte (delta PDte = -0.8 +/- 0.2 mV). The peritubular application of ouabain leads to a gradual, reversible and proportional decline of PDpt, PDNapt and mu Na+. Glucose induced delta PDpt and delta PDNapt decrease in parallel to PDpt and PDNapt, resp. In a separate series, the lumped conductance (Gm) of the luminal and basolateral cell membrane has been determined, which amounts to 2.4 +/- 0.3 microS/mm (tubule length). Gm decreases 23 +/- 4%, when PDpt is decreased to half.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ouabain on intracellular activities of K+, Na+, Cl-, H+ and Ca2+ in proximal tubules of frog kidneys

Using conventional and ion selective microelectrodes, the effect of ouabain (10(-4) mol/l) on peritubular cell membrane potential (PDpt), on intracellular pH (pHi) as well as on the intracellular ion activities of Cl- (Cli-), K+ (Ki+), Na+ (Nai+) and Ca2+ (Ca2i+) was studied in proximal tubules of the isolated perfused frog kidney. In the absence of ouabain (PDpt = -57.0 +/- 1.9 mV), the electrochemical potential difference of chloride (apparent mu Cl- = -22 +/- 2 mV) and of potassium (mu K+ = +24 +/- 3 mV) is directed from cell to bath, of H+ (mu H+ = -42 +/- 5 mV), of Na+ (mu Na+ = -102 +/- 4 mV) and of Ca2+ (mu Ca2+ = -148 +/- 6 mV) from bath to cell. Ouabain leads to a gradual decline of PDpt, which is reduced to half (PDpt, 1/2) within 31 +/- 4.6 min (in presence of luminal glucose and phenylalanine), and to a decline of the absolute values of apparent mu Cl+, of mu H+, mu Na+ and mu Ca2+. In contrast, an increase of mu K+ is observed. At PDpt, 1/2 apparent Cl-i increases by 6.2 +/- 1.0 mmol/l, pHi by 0.13 +/- 0.03, Ca2+i by 185 +/- 21 nmol/l, and Nai+ by 34.2 +/- 4.6 mmol/l, whereas Ki+ decreases by 37.7 +/- 2.2 mmol/l. The results suggest that the application of ouabain is followed by a decrease of peritubular cell membrane permeability to K+, by an accumulation of Ca2+, Na+ and HCO3- in the cell and by a dissipation of the electrochemical Cl- gradient.

Induction of chromosome aberrations and specific locus mutation but not sister chromatid exchanges in Chinese hamster ovary cells by neocarzinostatin

The induction of chromosome aberrations, sister chromatid exchanges (SCE), cytotoxicity, and 6-thioguanine-resistant mutation by neocarzinostatin (NCS) in Chinese hamster ovary cells was analyzed. It was observed that within the same concentration range of 0.01-0.1 mu/ml NCS, the drug induced a significant increase in all analyzed end-points except in SCE frequencies. There was no increase in SCE frequencies even when the cells were treated at the G1/S border in the first cell cycle and when aberrations were observed in the same cell showing a second cycle differential staining pattern. Our study indicates that the cellular damage induced by NCS leads to expression in chromosome aberrations, cytotoxicity, and mutagenicity but not in sister chromatid exchanges.

Immunoregulatory abnormalities in Evans syndrome

Immune function in six patients with Evans syndrome (Coombs-positive hemolytic anemia and immune thrombocytopenia) was compared to that in seven with chronic ITP. The two groups differed in measurements of T-cell subsets and immunoglobulin production. Evans syndrome patients had decreased T4 (T-helper) (P = 0.025), increased T8 (T-suppressor) (P = 0.008), and a decreased ratio of T4:T8 cells (P = 0.0009) when compared to controls. Results in chronic ITP patients were similar to those in controls. Serum IgG, IgM, and IgA levels and in vitro synthesis of IgG and/or IgM were decreased in most Evans syndrome patients. Diminished in vivo and in vitro immunoglobulin synthesis in Evans syndrome is consistent with the decreased T4:T8 ratio in these patients. The altered T4:T8 ratio may represent an unsuccessful response to an autoimmune process in which the trigger is unknown.

Keys to successful second toe-to-hand transfer: a review of 30 cases

Thirty cases of second toe-to-hand transfers are reported in which there were no failures. Factors judged to be important in these successful results include the careful choice of the donor site, distal to proximal exposure of first metatarsal artery, ensuring adequate perfusion of the toe before severing its vessels, and meticulous postoperative care.

Evidence for an amiloride sensitive Na+ pathway in the amphibian diluting segment induced by K+ adaptation

The effect of amiloride on cell membrane potentials and intracellular Na activity (Nai) was tested in early distal tubules of the isolated perfused kidney of control and of K-adapted (high-K diet) Amphiuma. Conventional and Na-sensitive liquid ion-exchanger microelectrodes were employed to measure the peritubular cell membrane potential (PDpt), the transepithelial potential difference (PDte) and the Na electrochemical gradient across the peritubular cell membrane (ENapt), in the absence and the presence of amiloride (1 X 10(-4) mol X 1(-1] in both groups of animals. Amiloride did not affect PDpt and ENapt in control animals but depolarized PDpt and ENapt by about 8 mV in K-adapted animals. Nai (11.0 +/- 0.6 mmol X 1(-1) in early distal cells of control animals) did not change significantly by this maneuver. However, Nai decreased to extremely low values (2.3 +/- 0.2 mmol X 1(-1] when the luminal cotransport system for Na, Cl and K was inhibited by the luminal application of furosemide (5 X 10(-5) mol/l) and when the luminal cell membrane was exposed simultaneously to amiloride. The amiloride-induced effects on PDpt, ENapt and Nai occurred within seconds and were fully reversible. We conclude that high-K diet (K adaptation) induces an amiloride-sensitive pathway in the luminal cell membrane of early distal cells of Amphiuma which exists in parallel with the furosemide-sensitive cotransport system located in this cell barrier. The results suggest a luminal amiloride-sensitive Na/H exchange mechanism which regulates the luminal K permeability.

Interaction of intracellular electrolytes and tubular transport

To disclose possible regulatory mechanisms, the potential difference across the peritubular cell membrane (PDpt) and intracellular activities of sodium (Nai+), potassium (Ki+), calcium (Cai2+), bicarbonate (HCO3i-) and chloride (Cli-) have been traced continuously during inhibition of Na+/K+-ATPase with ouabain. Within 31 +/- 4 min following application of ouabain, PDpt decreases (from 57 +/- 2 mV) to half and Ki+ by 37.7 +/- 2.2 mmol/l (from 63.5 +/- 1.9 mmol/l), Nai+ increases by 35.1 +/- 4.1 mmol/l (from 13.2 +/- 2.4 mmol/l), Cai2+ by 0.17 +/- 0.2 mumol/l (from 0.09 mumol/l), HCO3i-) by 3.0 +/- 1.1 mmol/l (from 15.3 +/- 2.0 mmol/l) and Cli- by 6.2 +/- 1.0 mmol/l (from 14.4 +/- 1.6 mmol/l). Within the same time the luminal and peritubular cell membrane resistances increase 45 +/- 15% and 53 +/- 17%, respectively. The increase of the resistances is mainly due to a decrease of K+ conductance, which in turn mainly accounts for the depolarisation of PDpt. Additional experiments demonstrate that the K+ conductance of the peritubular cell membrane is sensitive to the cell membrane potential difference and possibly linked to Na+/K+-ATPase activity. The decline of PDpt probably accounts for intracellular alkalinisation which in turn reduces Na+/H+ exchange. Na+-coupled transport of glucose and phenylalanine decrease in linear proportion to PDpt. The transport of these and probably of similar substances represents the main threat to electrolyte homeostasis of the cells.

Construction of penP delta 1, Bacillus licheniformis 749/C beta-lactamase lacking site for lipoprotein modification. Expression in Escherichia coli and Bacillus subtilis

Membrane-bound penicillinases in Gram-positive bacteria are glyceride-cysteine lipoproteins (Nielsen, J. B. K., and Lampen, J. O. (1982) J. Biol. Chem. 257, 4490-4495) that can be, but are not necessarily, intermediates in formation of exocellular enzymes. We have now deleted from the signal region of the Bacillus licheniformis 749/C beta-lactamase gene (penP) 15 base pairs that code for Ala-Leu-Ala-Gly-Cys. This sequence includes the Cys residue that undergoes lipophilic modification and the site of cleavage by signal peptidase and is well conserved in diverse prokaryotic lipoproteins. In the deletion gene, penP delta 1, the remaining Cys is preceded by 8 hydrophobic residues instead of 14 for the original modification site. PenP delta 1 has been cloned in Escherichia coli and Bacillus subtilis and its expression and products compared with penP. Penicillinase synthesis by penP delta 1 clones was greater than or equal to amounts formed by penP clones or B. licheniformis. Lipoprotein production from penP delta 1 was very low in either host and appears physiologically insignificant. In E. coli carrying penP delta 1, 25% of the penicillinase was released into the periplasm as a processed form. The remainder was a membrane-associated form of translation product size and was oriented to the periplasm. In mid-log cultures of B. subtilis carrying penP delta 1, the translation product and 2 protease-shortened species were present both in the cytoplasm and on the outer surface of the membrane. Release began at stationary phase and was dependent on the presence of enzyme processing to exo-small and a pH value greater than 7.5. We conclude that the shortened lipophilic sequence of the penP delta 1 prepenicillinase is adequate for transfer of the nascent chain through the membrane.

The effect of cAMP on the cell membrane potential and intracellular ion activities in proximal tubule of Rana esculenta

Experiments were performed in proximal tubule of the isolated perfused frog kidney to evaluate peritubular cell membrane potentials (PDpt), and the intracellular ion activities of sodium (Nai+), chloride (Cli-) and potassium (Ki+) under control conditions and following peritubular application of dibutyryl-cyclic AMP (cAMP, 2 X 10(-4) mol X 1(-1)). Conventional and ion-sensitive microelectrodes were applied to record continuously cAMP-induced changes of these parameters in individual proximal tubule cells. Within a few minutes a significant hyperpolarisation of PDpt (delta = 2.0 +/- 0.2 mV) occurs simultaneously with a decrease of Nai+ (delta = 2.5 +/- 0.5 mmol X 1(-1)). Ki+ increases (delta = 3.6 +/- 0.9 mmol X 1(-1)) and Cli- decreases (0.4 +/- 0.07 mmol X 1(-1)) slightly, but significantly. With both ions the alterations of the chemical gradient is significantly smaller than the potential shift. PDte is not significantly altered by cAMP. The cAMP-induced hyperpolarisation of PDpt can be observed in presence and absence of luminal glucose. However, omission of Na+ from the luminal perfusate abolishes the hyperpolarising effect of cAMP on PDpt. The results suggest that cAMP reduces sodium entry from the lumen into the cell, thus hyperpolarising the cell membrane and decreasing Nai+. Persistence of sensitivity of PDpt to cAMP after omission of glucose indicates that other Na+ coupled transport processes and/or passive Na+ conductance are affected by cAMP. the changes of Ki+ and Cli- are secondary, following the change of PDpt.

Effect of luminal potassium on cellular sodium activity in the early distal tubule of Amphiuma kidney

From previous studies it is known that a furosemide-sensitive sodium chloride cotransport system is operative in the luminal cell membrane of the early distal amphibian tubule. Since inhibition of sodium chloride cotransport prevents potassium reabsorption in this nephron segment, experiments were carried out to evaluate further the possible relationship between sodium chloride and potassium transport by studying the changes of cellular sodium activity following luminal deletion of potassium ions. Sodium-sensitive liquid ion exchange microelectrodes and conventional microelectrodes were employed to determine the transepithelial potential (PDte), the peritubular cell membrane potential (PDpt) and the intracellular sodium activity (Nai+) in the presence and absence of luminal potassium. The ratio of the luminal cell membrane resistance over the peritubular cell membrane resistance (Rlu/Rpt) was also estimated. When potassium ions are omitted from the luminal perfusate, PDpt hyperpolarizes by some 20 mV, PDte approaches zero and Nai+ decreases by about 40%. Rlu/Rpt is more than doubled in the presence of a potassium-free perfusate. Both potential and resistance changes are fully reversible. Similar results were obtained in experiments in which Barium ions (1 mmol/1 BaCl2) were present during the luminal potassium substitution. Our results indicate that absence of potassium inhibits luminal sodium chloride entry; as a result of continued peritubular sodium extrusion cellular sodium activity falls. The increase of Rlu/Rpt following perfusion with a potassium-free perfusate is interpreted as a decrease of a significant electrodiffusive potassium conductance in the luminal cell membrane.

Cellular Mechanism of the furosemide sensitive transport system in the kidney

Experiments were performed in the distal tubule of the doubly-perfused kidney of Amphiuma to determine active and passive forces, involved in the transport processes of potassium, sodium and chloride. Ion-sensitive microelectrodes and conventional microelectrodes were applied to estimate intracellular ion activities, cell membrane potentials and net flux of potassium and chloride under control conditions and during inhibition of active transport. Sodium chloride cotransport, located in the luminal cell membrane is postulated, based on the following observations: Total omission of sodium from the tubular lumen inhibits furosemide sensitive chloride reabsorption, decreases the lumen positive transepithelial potential difference and leads to a dramatic decrease of intracellular chloride. The experiments further suggest that potassium ions are involved in the sodium chloride transport system because potassium reabsorption is inhibited by furosemide and because intracellular sodium falls significantly when potassium ions are removed from the tubular fluid. Furthermore, there is experimental evidence that the luminal potassium uptake mechanism is suppressed after potassium adaptation. Under these conditions potassium transport is found to be insensitive to furosemide. The data suggest a furosemide sensitive cotransport system for sodium, chloride and potassium, operative in the luminal cell membrane. The energy for this carrier-mediated transport process is provided by the large "downhill" gradient of sodium across the luminal cell membrane which is maintained by the sodium pump located in the peritubular cell membrane.

Microvasculature of human colorectal epithelial tumors. An electron microscopic study

The ultrastructure of the microvasculature in human colorectal adenomas and carcinomas was studied, and compared with that of normal tissue. Blood vessels in adenomas were generally of normal structure, whereas carcinoma vessels displayed a variety of structural alterations. Endothelial proliferation was frequently observed in all the eleven carcinomas examined, which confirms the reports of new vessel formation in experimental malignant tumors. The presence of fenestrations in obviously abnormal endothelium was tentatively attributed to hypoxia, vascular regression or immaturity of the cells, in spite of the fact that normal capillaries in colonic mucosa are fenestrated. Some vessels showed multilayered basement membranes, various types of activated cells containing numerous lysosomal granules, and thickened perivascular tissue. These features may be a vascular response to repeated damage or a manifestation of vascular remodelling. Dilated thin-walled vessels, which were usually found at the periphery of carcinomas, were identified as venules. Small vessels located between the closely apposed carcinoma tubules were not obviously abnormal. They were nevertheless considered to be tumor-induced vessels which had undergone differentiation. The differences in vascular morphology between adenomas and carcinomas were considered to be due to their different growth patterns, growth rates and degrees of maturity.

Effects of inhibition of chloride transport on intracellular sodium activity in distal amphibian nephron

Previous experiments had demonstrated that cell chloride activities in early distal tubule cells of Amphiuma are above equilibrium distribution. Chloride activities fell sharply towards electrochemical equilibrium following perfusion of the tubular lumen with furosemide or with sodium-free solutions. These results suggested a furosemide-sensitive sodium chloride cotransport system in the luminal cell membrane. The present experiments were carried out to evaluate directly the electrochemical driving forces acting on sodium ions under similar experimental conditions. Intracellular sodium activity measurements were performed in the doubly-perfused kidney of Amphiuma by means of single-barreled liquid ion-exchange microelectrodes. Basolateral cell membrane potential and resistance ratio measurements of tubular cell membranes were also carried out under control conditions and after inhibition of chloride transport by luminal application of furosemide (5 . 10(-5) mol/l) or by omission of chloride. Control conditions were characterized by a steep downhill electrochemical gradient for sodium ions from lumen to cell. Inhibition of chloride transport led to a sharp decrease of intracellular sodium activity and to hyperpolarization of the peritubular membrane potential while the resistance ratio of the tubular cell membranes did not change significantly. These results demonstrate the presence of low cellular sodium activities in early distal tubule cells. The sharp decline of cell sodium after furosemide and after luminal chloride removal is consistent with inhibition of a sodium chloride cotransport system and continued peritubular sodium extrusion. The latter can increase the electrochemical gradient of sodium ions beyond that observed under control conditions.

The free forearm flap--a report of 25 cases

In 25 cases using microvascular techniques, free forearm flaps were used for reconstruction of various tissue defects. 15 flaps were used for repair of hand injuries, 5 for facial defects, 1 for lower extremity deformity and 4 for total rhinoplasty. All flaps survived. The arterial blood supply of the forearm flap comes from the cutaneous branches of the radial artery while its venous drainage is via cephalic vein and the radial comitantes veins. The forearm flap has a thin layer of subcutaneous fatty tissue, can provide quite large area of soft tissue and the vascular pedicle is long with moderately large calibre vessels. The donor area, however, has to be skin grafted, leaving an unsightly scar over the forearm which is one of the shortcomings of this flap. Secondly it means sacrificing a major arterial supply to the hand on the donor side.

Hereditary elliptocytosis: morphologic abnormalities during acute hepatitis

A 10-year-old black girl with hereditary elliptocytosis had a transient increase in hemolysis and unusual red cell morphologic changes during an episode of acute hepatitis. Changes in membrane lipids of these elliptocytes with defective membrane skeletal protein and abnormal distribution of cholesterol may be responsible for this phenomenon.

Evans syndrome in childhood

The combination of idiopathic thrombocytopenic purpura and autoimmune hemolytic anemia is rare in childhood. Among 164 instances of ITP and 15 instances of AHA, 11 patients were found to have this combination. Three were found to have systemic lupus erythematosus, one had aplastic anemia, and seven had Evans syndrome. Neutropenia, at times associated with bacterial infections, occurred in four of the latter patients. Unlike most cases of ITP or AHA in childhood, the clinical course of Evans syndrome is usually chronic and relapsing. Treatment including corticosteroids, splenectomy, and immunosuppressive agents has been generally unsatisfactory. In view of the frequent presence of antibodies directed at red blood cells, platelets, neutrophils, and lymphocytes, immunopancytopenia may be a better term for this condition.

Three new yellow loci in Chlamydomonas reinhardtii

Three phenotypically 'yellow', mendelian mutants of Chlamydomonas reinhardtii have been isolated and tested for allelism with the yellow mutant y-1 a1 and with each other. The three mutants represent three new yellow loci, two of which are located on linkage group I. Like y-1a, the mutants accumulate protochlorophyllide when grown under dim light, but have a wildtype phenotype when grown in the light. We conclude that the control of light-independent protochlorophyllide reduction is more complex than has been thought previously.

Free transfer of the second toe combined with dorsalis pedis flap using microvascular technique for reconstruction of the thumb and other fingers

The blood supply to the dorsum of the feet was studied in 100 cadaver feet specimens. The understanding of anatomical variation of branches of dorsalis pedis artery and its venous system are important in determining the success of the operation for free toe or dorsalis pedis flap transplantation. Three groups of fine branches of arterial system supplying the skin on the dorsum of the feet are classified; the central, the intermediate and the marginal groups. The central group is the dorminant blood supply to the dorsalis pedis skin flap. The first dorsal metatarsal artery which is a main branch of the dorsalis pedis artery remains to be dominant feeding artery to the second toe. From these cadaver specimens, three types of distribution are formulated, but with different percentages of distribution as compared with that of Gilbert's data. Seven consecutive cases of the second toe combined with dorsalis pedis flap transfer using microvascular technique for the reconstruction of thumb and other fingers are reported. The operation is designed to meet the demand of one stage reconstruction of the missing thumb or other fingers which are associated with surrounding soft tissue defects. Preparatory soft tissue repair by skin flap or tube flap is thus obviated.

Genetic control of chlorophyll biosynthesis in chlamydomonas: analysis of a mutant affecting synthesis of delta-aminolevulinic acid

A Mendelian mutation, r-1, in Chlamydomonas reinhardtii has been isolated which elevates protoporphyrin accumulation of the Mendelian protoporphyrin mutants brS-1 and brC-1 more than 20 fold. This increased protoporphyrin accumulation is shown to result from increased delta-aminolevulinic acid synthesis in the double mutants brS-1 r-1 and brC-1 r-1 over that of brS-1 and brC-1 alone. By itself, the r-1 mutation has no detectable protoporphyrin accumulation and has reduced levels of delta-aminolevulinic acid synthesizing activity, chlorophyll, protoheme, and cytochrome oxidase activity. The low levels of chlorophyll and protoheme in r-1 can be increased by feeding delta-aminolevulinic acid. We hypothesize that r-1 may be a mutation of the gene coding for the delta-aminolevulinic acid synthesizing enzyme which reduces the sensitivity of this enzyme to feedback inhibition by protoporphyrin or heme as well as reducing the overall activity of the enzyme. Evidence is also presented for a single delta-aminolevulinic acid synthesizing enzyme serving both chlorophyll and heme biosynthesis.

Encephalopathy associated with occult neuroblastoma

✓ The authors report four cases of occult neuroblastoma in children with the striking clinical findings of opsoclonus, myoclonus, and ataxia. The diagnostic value of plain roentgenograms of the chest and abdomen or an intravenous pyelogram is emphasized. Assays for vanillyl mandelic acid and cystathionine may be of value. The clinical course and pathogenesis of encephalopathies due to neuroblastoma are discussed.