Micropuncture study of the renal responses of the urodele amphibian Necturus maculosus to injections of arginine vasotocin and an anti-aldosterone compound

1. Necturus maculosus kidney function has been examined using standard clearance techniques and renal tubular micropuncture methodology. 2. Throughout, cyanocobalamin (vitamin B12) has been used to monitor glomerular filtration rate (GFR) and tubular water movements. It was established that this substance was handled by the Necturus kidney in a similar manner to inulin. It can be readily analysed, together with renal electrolytes, by electron microprobe techniques. 3. Profiles of transtubular gradients (TF:P ratios) along the nephron were established for osmolarity, sodium, potassium, calcium and cobalt (of cyanocobalamin). 4. Ureteral urine is always hyposmotic with respect to plasma and the site of dilution of the plasma ultrafiltrate is within the distal segment. 5. Up to 30% of the filtrate is isosmotically reabsorbed along the proximal tubule; the tubular fluid:plasma ratio for osmolarity and sodium is around 1, and the TF:P for cobalt of cyanocobalamin is about 1.4 by the end of this segment. 6. The renal effects of the neurohypophysial hormone arginine vasotocin (AVT) and an aldosterone antagonist (SC14266; Soldactone) have been examined. 7. AVT was consistently antidiuretic causing both a decreased GFR and an enhanced distal tubular reabsorption of water. 8. SC14266 also increased distal tubular reabsorption of water. Such an effect differs from that found in higher vertebrates, and may indicate a “glucocorticoid-type” of renal action for aldosterone in amphibians.

Human X-Linked genes regionally mapped utilizing X-autosome translocations and somatic cell hybrids

Human genes coding for hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase), glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49; D-glucose-6-phosphate:NADP+ 1-oxidoreductase), and phosphoglycerate kinase (PGK, EC 2.7.2.3; ATP:3-phospho-D-glycerate 1-phosphotransferase) have been assigned to specific regions on the long arm of the X chromosome by somatic cell gentic techniques. Gene assignment and linear order were determined by employing human somatic cells possessing an X/9 translocation or an X/22 translocation in man-mouse cell hybridization studies. The X/9 translocation involved the majority of the X long arm translocated to chromosome 9 and the X/22 translocation involved the distal half of the X long arm translocated to 22. In each case these rearrangements appeared to be reciprocal. Concordant segregation of X-linked enzymes and segments of the X chromosome generated by the translocations indicated assignment of the PGK gene to a proximal long arm region (q12-q22) and the HPRT and G6PD genes to the distal half (q22-qter) of the X long arm. Further evidence suggests a gene order on the X long arm of centromere-PGK-HPRT-G6PD.

A familial F/G translocation [t(p-; 22q+)] observed in three generations

A family is described in which a translocation between chromosomes 20 and 22 has been observed in three generations. Two first cousins with remarkably similar malformations and mental retardation have identical karyotypes which, after chromosome banding, were interpreted as partially trisomic for the short arm of chromosome No. 20.

The distribution and localization of drug-induced secondary constrictions in human chromosomes

BUdR, mitomycin C and hydroxylamine hydrochloride induce secondary constrictions in particular human chromosomes. The increased frequency of constriction formation in certain chromosomes is time and drug dependent, and correlates well with the timing of DNA synthesis. The frequency at which some of these constrictions can be induced by specific drugs at specific times increases the usefulness of these landmarks in chromosome identification.

Observations on Aeromonas hydrophila septicaemia in a patient with leukaemia

A Gram-negative bacillus isolated from the blood of a leukaemic patient with septicaemia was identified on the basis of common tests as Escherichia coli. However, the organism's antibiogram was atypical of E. coli and led to its re-examination and correct identification as Aeromonas hydrophila. A. hydrophila is sensitive to chloramphenicol and tetracycline, characteristics useful in differentiation from E. coli. A simple test differentiating this organism from the Enterobacteriaceae is the oxidase test. A. hydrophila is oxidase positive.