In vitro effects of parathyroid hormone on kidney cortical slices: cAMP responses and concomitant inhibition of the Na+ gradient-dependent uptake of phosphate by brush border membrane vesicles isolated from the renal slices

Mouse renal cortical slices were incubated with parathyroid hormone (30 U/ml) for 2 min. Brush border membrane vesicles isolated from the treated slices had a decreased Na+ gradient-dependent uptake of phosphate. Concomitantly, the hormone elicited the activation of adenylate cyclase, the increase in tissue level of cAMP, and the enhancement of cAMP-dependent protein kinase.

Gentamicin uptake by renal tubule brush border membrane vesicles

The uptake of [3H]gentamicin by isolated rabbit renal proximal tubule brush border membrane vesicles was studied. Uptake was biphasic, with an initial rapid uptake followed by a prolonged slower phase. Approximately half of the total uptake represented binding; the other half represented transport into an intravesicular space. Scatchard analysis indicated the presence of two binding sites, differing in affinity (8 X 10(3) and 0.9 X 10(3) M-1) and number of sites per milligram of protein (1.2 and 3.7 nmol/mg of membrane protein, respectively). [3H]Gentamicin uptake was not affected by a Na+ electrochemical gradient, a valinomycin-generated (inside negative) K+ diffusion potential or the presence of phlorizin and D- of L-glucose. These findings indicate that the mechanism of uptake of the aminoglycoside was distinct from those of sugar and amino acids. Uptake of [3H]gentamicin was inhibited and reversed by the unlabeled aminoglycoside and by spermine. Spermine, on a molar basis, was as effective as gentamicin. These results suggest that gentamicin and spermine may have a common polyamine transport system and demonstrate the feasibility of further investigations to prevent aminoglycoside accumulation and possibly subsequent nephrotoxicity.

Pheochromocytoma in rats: incidence, etiology, morphology and functional activity

The incidence of spontaneous pheochromocytoma in rats varies with the strain, sex, age and diet of the animals. Treatment with growth hormone, estrogens, or radiation is associated with the occurrence of pheochromocytoma in the rat. Histological evidence and transplantation studies indicate that pheochromocytoma in rats possesses a low grade of malignancy. A transplantable radiation-induced pheochromocytoma model has been shown to be functionally active.

Urinary tract calculi in man and laboratory animals: incidence, composition, and etiology

Calculi in the urinary tract is a disease which afflicts not only man, but also experimental animals. The incidence of human stone disease varies widely according to the geographical area. With the advent of sophisticated physicochemical techniques, the elucidation of structure and the quantification of mineral components of urinary calculi have been greatly facilitated. In addition to calcium oxalate and calcium phosphate, more than ten other minerals and a large number of trace elements have been identified to date. Matrix material consists of such macro-molecules as proteins and mucopolysaccharides. The etiology of urinary calculi is varied; diet, drugs, chemicals, bladder implants, infections, metabolic derangements, and environmental influences are some of the factors that can contribute to the pathogenesis of stones. The literature findings reflect the complexity of urolithiasis as a clinicopathological problem.

Distribution and environmental synchronization of the marine insect, Halobates robustus, in the Galapagos islands

The following three aspects of the biology of the marine insect Halobates robustus were studied, during a two week observation period, at several sites in the Galapagos Islands: distribution, aggregation behaviour and rhythmicity of locomotory activity. H. robustus occurred in highest numbers on the water surface at shores fringed with mangroves. The aggregations of H. robustus varied according to their location and density. Copulating adults formed dense, floating aggregations, which tended to be close to rocks or mangroves. Late instar nymphs were less aggregated and, in lagoons (where there was some shelter from direct tidal forces), were furthest from the shore. In two types of habitat (mangrove-fringed, sandy shores and rocky shores) the aggregations of H. robustus showed a pronounced ability to maintain a floating station in relation to the surrounding environment, irrespective of tidal movements (in one case at 34 m from the nearest fixed objects). Evidence of the ability of the aggregations to maintain station on the water surface was also obtained by comparing the movements of H. robustus with those of floating polystyrene particles, which move passively with wind and tide. Laboratory observations and experiments indicated no clear periodicity in locomotory movements throughout a 24 h period. However, the frequency of encounters between individuals showed two daily peaks, post-dawn and pre-dusk, with fewer encounters during the day and only occasional encounters during the night. By shifting the light-dark cycle it was demonstrated that the daily bimodal rhythm of encounters is triggered by dawn and, since it is not maintained in constant light or dark, an 'hour-glass' mechanism is suggested. The contributions of single adults, of copulating pairs and of immature stages to the overall pattern of activity were also determined. Immature stages did not affect the overall rate of encounters significantly and the interactions between single and copulating pairs of adults appear to have been responsible for the bimodal pattern.

Who does what? Role definition in a psychiatric hospital

This is a report of an interdisciplinary workshop which was held to define the roles of different disciplines within a psychiatric unit. While the report emphasizes the medicolegal responsibility of the psychiatrists, we found, in a review of the knowledge background of the several disciplines, potentials for a further utilization of the knowledge which is acquired during their training. Meeting the patient's needs is the prime factor in determining the roles of the disciplines. The needs of the patient have expanded. Each discipline has both an exclusive role and an inclusive role. One important result of the workshop was the warmth and the esprit de corps that was felt afterwards.

The Münchausen syndrome as a psychiatric condition

In this presentation of two cases it is suggested that many Münchausen syndrome patients present with psychiatric symptoms. This syndrome, however, should be differentiated from other clinical psychiatric conditions.

Comparative stereochemistry in the aziridine ring openings of N-methylmitomycin A and 7-methoxy-1,2-(N-methylaziridino)mitosene

A useful method was found for the conversion of mitomycin C into N-methylmitomycin A. The latter compound gave only two products on acid hydrolysis, the cis- and trans-1-hydroxy-7-methoxy-2-methylaminomitosenes. This selectivity allowed the cis--trans ratio to be quantitatively determined as 4:1. Such a predominance of the cis isomer is unexpected in view of the trans stereochemistry obtained in the opening of simple aziridines. In order to determine if the 9a-methoxy group of mitomycins controlled the direction of aziridine ring opening 7-methoxy-1,2-(N-methylaziridino)mitosene, which lacks this substituent, was prepared and hydrolyzed in acid. It gave the same two products in a 3:1 cis-trans ratio. In the induction of lambda-bacteriophage in Escherichia coli cis-1-hydroxy-7-methoxy-2-methylaminomitosene was more active than the corresponding trans isomer, but both of these compounds were less active than the aziridinomitosene or the mitomycins. Mitomycin A, mitomycin C, and N-methylmitomycin A were active against P388 leukemia in mice.

Mechanism of the irreversible inhibition of aspartate aminotransferase by the bacterial toxin L-2-amino-4-methoxy-trans-3-butenoic acid

The naturally occurring toxin L-2-amino-4-methoxy-trans-3-butenoic (AMB) acid irreversibly inhibits pyridoxal phosphate-linked aspartate aminotransferase. The inhibitor is a substrate for the enzyme, and as such is converted into a highly reactive intermediate which chemically reacts with an active site residue, thus irreversibly inactivating the enzyme. Enzymological and model studies on AMB are presented which enable one to determine the precise mechanism of action of this toxin. The mechanism involves Schiff base formation between the enzyme and toxin followed by alpha-C--H bond cleavage and aldimine isomerization to generate a bifunctional Michael acceptor. This molecule alkylates an active site residue by an addition and elimination route.

Electrical Measurement of Flow Rate of Pulverized Coal Suspension

Electrostatic probes for indicating instantaneous flow rate of pulverized coal suspension in a pipe were devised and tested. Experiments were performed on flow systems consisting of 2 and 5-in-ID pipes with mass flow ratios up to 0.66 lb of coal/lb of air at up to 115 fps air velocity. Calibrations were made with a differential isokinetic sampling technique. With accurate control of probe potential, consistent indication of electrostatic ball probes (1/4 to 1/2-in. dia) was at the 10−7 amp level and at 10−8 amp level with cylindrical probes (0.2-in. ID). Accuracy within 1 percent was demonstrated to be feasible. Since the probe output is an electrical signal, this device makes integrated control system including the coal line feasible. Further, instantaneous and accurate fuel adjustment into furnaces facilitates air-pollution control.