Joseph R. Davis

A comparison of the stimulatory effects of cadmium and zinc on normal and lead-inhibited human erythrocytic δ-aminolevulinic acid dehydratase activity in vitro

Abstract Zinc has been reported to activate δ-aminolevulinic acid dehydratase (ALAD) and to reverse lead-induced inhibition of human blood ALAD activity in vitro . Inasmuch as cadmium lies just below zinc in Group IIB of the periodic table of elements, similar studies were initiated with cadmium. Using normal adult human whole blood hemolysates, cadmium was found to activate normal erythrocytic ALAD and to reverse the in vitro lead-induced inhibition of ALAD at concentrations 40- to 100-fold lower than those of zinc. At higher concentrations cadmium was observed to inhibit erythrocytic ALAD activity, with a 50% inhibition of ALAD activity occurring at a concentration approximately 20 times higher than that of lead. The inhibition caused by cadmium, unlike that caused by lead, could not be reversed by an in vitro addition of zinc. The present results indicate that, with respect to concentration, cadmium is a more potent activator of normal adult human erythrocytic ALAD activity than is zinc. It is suggested that the role of cadmium and zinc in increasing ALAD activity and reversing lead induced inhibition of ALAD activity is a structural one related to binding of the metal to peripheral sulfhydryl groups.

Pharmacological Studies on the Testicular Capsule in Relation to Sperm Transport

The testicular capsule, which forms the thin outer covering of the testis, has long been considered an inert tissue with no other function than to contain the underlying seminiferous tubular mass. In the course of carrying out in vitro metabolic studies on rat testicular tissue in our laboratory, we have continually peeled off and discarded the capsule of the testis prior to slicing the testis with a Stadie-Riggs microtome. It recently occurred to us, however, that it might be quite easy to prepare and save the capsule of the rat testis as an intact tissue provided one first removed the seminiferous tubules from the interior of the organ (1).

Correlation of the physicochemical properties of metal ions with their activation and inhibition of human erythrocytic δ-aminolevulinic acid dehydratase (ALAD) in vitro ☆

Abstract Using normal adult human whole blood hemolysates this study determined, in a dose-response fashion, the in vitro effects of Na+, Mg2+, Al3+, Mn2+, Cu2+, Ag+, Zn2+, Cd2+, Hg2+, Ga3+, In3+, Sn2+, Sn4+, and Pb2+ on normal erythrocytic ALAD. The effects of these 14 metal ions on erythrocytic ALAD 50% inhibited by Pb2+ were also determined as was the ability of a maximum stimulatory concentration of Zn2+ to prevent or reverse the effects of these metal ions on erythrocytic ALAD. The effects of these metal ions were then classified in terms of their oxidation state, characteristic coordination number, coordination geometry, and hard and soft Lewis acid characteristics in order to determine the physical and chemical properties associated with the ability of a metal ion to activate or inhibit erythrocytic ALAD and whether these properties are unique to a single metal ion. Preincubation studies established Zn2+ to be the only metal ion to both activate erythrocytic ALAD and to prevent or reverse the Pb2+-induced inhibition of erythrocytic ALAD in vitro even after prolonged contact with the enzyme. Therefore future investigations of the use of nontoxic salts of Zn2+ as a prophylactic agent or therapeutic adjunct in the prevention or treatment of lead poisoning with its possibly toxic accumulation of ALA are proposed.

Species variation in the effect of temperature on the incorporation of l-lysine-U-C14 into protein of testis slices

Abstract 1. 1. The incorporation of l -lysine -U- C 14 into protein of slices of testes of the adult rat, mouse, hamster, rabbit, guinea pig and dog has been studied following a 1 hr incubation period at temperatures of 26, 32, 37·5 and 44°C. 2. 2. In the rat, mouse and hamster, maximal incorporation of radioactive lysine into testicular protein occurred at 32°C. 3. 3. In the rabbit, guinea pig and dog, maximal incorporation of isotope into testicular protein occurred at 37·5°C. 4. 4. Measurements of the testicular temperatures of the rat, mouse and hamster were found to be lower than the corresponding testicular temperatures of the rabbit, guinea pig and dog. 5. 5. The data obtained indicate that optimal activity for testicular protein labeling from radioactive lysine in each species occurs at a temperature which is closest to that normally found in the scrotal sac of each animal.

Rapid colorimetric determination of adenine compounds

Abstract A procedure for both a rapid qualitative and a quantitative determination for adenine in a mixture of various purines and pyrimidines is described. In addition, the method can also be applied for the rapid detection and quantitative estimation of a number of adenine nucleosides and nucleotides without prior hydrolysis of these compounds.

Effect of nitrofurazone on the incorporation of l-lysine-U-14C into protein of rat testis☆

Abstract The nitrofuran group of chemotherapeutic agents has long been known to exert specific histological changes in the testicular germinal epithelium of the rat, 1 mouse, 2 and dog. 3 These changes involve the arrest of spermatogenesis at the primary spermatocyte stage. 4 The histological architecture of the nitrofuran-treated testis of the rat therefore closely resembles that of the cryptorchid rat testis in being characterized by a virtual absence of all the spermatids and mature spermatozoa. Recent data from this laboratory have indicated that the induction of experimental cryptorchidism in the rat results in a marked increase in the incorporation of l -lysine-U- 14 C into protein of the remaining cells of the seminiferous germinal epithelium. 5,6 It appears that the loss of spermatids and spermatozoa from a nitrofuran-treated testis offers a unique opportunity to make a selective study of protein labeling of the remaining cells of the seminiferous epithelium as they exist in the natural environmental temperature of the scrotal sac rather than as they exist after exposure to the higher environmental temperature of the abdominal cavity as is necessarily the case in experimental cryptorchidism. The present studies were therefore designed to investigate the incorporation of radioactive lysine into protein of the remaining cells of the testis after the oral administration of nitrofurazone to adult rats.

Developmental changes in delta-aminolevulinic acid dehydratase (ALAD) activity and blood reticulocyte percent in the developing rat. A brief note.

A correlation between blood reticulocyte percent and the activity of erythrocytic delta-aminolevulinic acid dehydratase (ALAD) in the developing rat has been established during the progression from a state of macrocytic hypochromic anemia at birth to a normocytic normochromic state at puberty, and finally to a state just prior to adulthood at which the reticulocyte percent had stabilized. Both reticulocyte percent and erythrocytic ALAD activity was found to decrease with age, rapidly at first until a normocytic normochromic state was reached at puberty and then more slowly until just before adulthood when both plateaued. A direct, linear correlation between erythrocytic ALAD activity and blood reticulocyte percent was found with a P value of less than 0.001. These findings should be carefully considered when using the rat as a model for lead poisoning and possibly for other disorders of heme biosynthesis.

A comparison of the cellulose acetate electrophoretic serum lipoprotein-cholesterol profile of the adult male rat with other species

A comparison was made of the serum lipoprotein-cholesterol profile, obtained by cellulose acetate electrophoresis coupled with an enzymatic stain for total cholesterol, of the adult male rat, mouse, rabbit, dog, monkey and human. Four cholesterol-staining lipoprotein bands were detected in rat serum, while only three cholesterol-staining lipoprotein bands were present in the other species studied. The apparently unique lipoprotein-cholesterol band in the rat was found to electrophoretically migrate in the prealbumin region of rat serum, has been named prealbumin lipoprotein-cholesterol (PAL-C) and was shown to be a high density lipoprotein (HDL). Of the species studied those more susceptible to experimentally induced atherosclerosis had higher low density lipoprotein-cholesterol to HDL-cholesterol ratios compared to those species least susceptible to experimentally induced atherosclerosis.

Effect of ageing on the response of the rat isolated testicular capsule to norepinephrine, acetylcholine and prostaglandins

The response of the rat isolated testicular capsule to norepinephrine (NE), acetylcholine (ACh) and prostaglandins (PG) was found to be age-dependent. The testicular capsular contractions attributable to smooth muscle cells located within the tunica albuginea may be involved in the transport of non-motile spermatozoa from the testis and into the epididymis. With an increase in age of the age of the rat there was a concomitant increase in mass of the testis, thickness of the capsule and the amount of smooth muscle fibers present in the tunica albuginea. The response to the addition of equimolar concentrations of NE and PGA2 became progressively greater as the age of the animal increased. However, the response of the testicular capsule to ACh remained constant throughout adulthood, while PGF2 alpha became progressively less stimulatory as the age of the animal increased. These findings suggest that neurohumoral agents may have an important role in the maintenance of testicular capsular contractions with regard to ageing.

A comparison of the aerobic and anaerobic incorporation of -lysine-U-C14 into protein of various tissues of the rat

Abstract 1. 1. A comparison of the in vitro capacities of nineteen tissues of the adult rat to incorporate l - lysine -U- C 14 into protein has been carried out in the presence of 0·009 M glucose. 2. 2. The highest degree of incorporation of radioactive lysine into protein under aerobic conditions occurred in samples of bone marrow. 3. 3. The highest degree of incorporation of radioactive lysine into protein under anaerobic conditions occurred in samples of lymph node.