Slow Orthograde Axonal Transport of Radiolabelled Protein in Sciatic Motoneurones of Rats with Short-Term Experimental Diabetes: Effects of Treatment with an Aldose Reductase Inhibitor or myo-Inositol

Abstract: This study examined the effect of streptozotocin diabetes of 5 weeks duration on the profile of slow orthogradely transported radiolabelled protein in rat sciatic motoneurones. The diabetic rats showed a retardation of the tail of the slow-component profile. This selective retardation was unaffected by treatment with an aldose reductase inhibitor, although this treatment reduced the accumulation of sorbitol and prevented the depletion of myo -inositol in the sciatic nerves of the treated diabetic rats. Other groups, treated with myo -inositol, had normal or elevated sciatic nerve myo -inositol levels in the presence of accumulated sorbitol. The axonal transport profiles from both control and diabetic myo-inositol-treated groups gave normal tail velocities but an altered shape such that retardation of the tail of the profile may have been present in both. The study concludes that rats with 5 weeks streptozotocin diabetes show retardation of the velocity of the most slowly transported proteins in sciatic motoneurones, and that this defect is not linked to the polyol pathway.     

Induction of tumors and generation of recovered sarcoma viruses by, and mapping of deletions in, two molecularly cloned src deletion mutants.

td108 , a transformation-defective (td) deletion mutant of the Schmidt-Ruppin strain of Rous sarcoma virus of subgroup A (SR-A), was molecularly cloned. Two isolates of td viruses, td108 -3b and td108 -4a, obtained by transfection of the molecularly cloned td108 DNAs into chicken embryo fibroblasts, were tested for their ability to induce tumors and generate recovered avian sarcoma viruses ( rASVs ) in chickens. Both td viruses were able to induce tumors with a latency and frequency similar to those observed previously with biologically purified td mutants of SR-A. rASVs were isolated from most of the tumors examined. The genomic RNAs of those newly obtained rASVs were analyzed by RNase T1 oligonucleotide fingerprinting. The results showed that they had regained the deleted src sequences and contained the same set of marker src oligonucleotides as those of rASVs analyzed previously. The src oligonucleotides of rASVs are distinguishable from those present in SR-A. We conclude that those rASVs must have been generated by recombination between the molecularly cloned td mutants and the c-src sequence. The deletions in the td mutants were mapped by restriction enzyme analysis and nucleotide sequencing. td108 -3b was found to contain an internal src deletion of 1,416 nucleotides and to retain 57 and 105 nucleotides of the 5' and 3' src coding sequences, respectively. td108 -4a contained a src deletion of 1,174 nucleotides and retained 180 and 225 nucleotides of the 5' and 3' src sequences, respectively. Comparison of sequences in the 5' src and its upstream region of td108 -3b with those of SR-A, rASV1441 (a td108 -derived rASV analyzed previously), and c-src suggested that the 5' recombination between td108 and c-src occurred from 7 to 20 nucleotides upstream from the beginning of the src coding sequence.     

Biological activity assessment of the vitamin D metabolites 1,25-dihydroxy-24-oxo-vitamin D3 and 1,23,25-trihydroxy-24-oxo-vitamin D3

Two new metabolites of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], namely 1,25(OH)2-24-oxo-vitamin D3 and 1,23,25(OH)3-24-oxo-vitamin D3, have been prepared in vitro using chick intestinal mucosal homogenates. To investigate the binding of 1,25(OH)2-[23-3H]-24-oxo-D3 and 1,23,25(OH)3-[23-3H]-24-oxo-D3 to the chick intestinal receptor we have isolated both metabolites in radioactive form using an incubation system containing 1,25(OH)2-[23,24-3H))-D3 with a specific radioactivity of 5.6 Ci/mmol. Both metabolites were highly purified by using Sephadex LH-20 chromatography followed by high-pressure liquid chromatography (HPLC). Sucrose density gradient sedimentation analysis showed specific binding of both tritium-labeled metabolites to the chick intestinal cytosol receptor. Experiments were carried out to determine the relative effectiveness of binding to the chick intestinal mucosa receptor for 1,25(OH)2D3. The results are expressed as relative competitive index (RCI), where the RCI is defined as 100 for 1,25(OH)2D3. Whereas the RCI obtained for 1,25(OH)2-24-oxo-D3 was 98 +/- 2 (SE), the RCI for 1,23,25(OH)3-24-oxo-D3 was only 28 +/- 6 (SE). Also, the biological activity of both new metabolites was assessed in vivo in the chick. In our assay for intestinal calcium absorption, 1,25(OH)2-24-oxo-D3 was active at a dose level of 1.63 and 4.88 nmol/bird (at 14 h), whereas 1,23,25(OH)3-24-oxo-D3 showed only weak biological activity in this system. In our assay for bone calcium mobilization, administration of both new metabolites showed modest activity at the 4.88-nmol dose level, which was reduced at the 1.63-nmol dose level. The results indicate that biological activity declines as 1,25(OH)2D3 is metabolized to 1,24R,25(OH)3D3, 1,25(OH)2-24-oxo-D3, and then 1,23,25(OH)3-24-oxo-D3.     

Observations on some environmental factors connected with fertility in heat stressed cows

A field study was performed using 15 Kibutz dairy herds, in which 4195 cows situated in northern Israel were milked to determine the influence of climatological factors and nutritional regimes on the conception rate during the summer period (July-September). The Overall Conception Rate (OCR) during summer was 28.2% (17.3-41.9%) compared to 40% in the spring (May-June). The conception rate from first inseminations (CRl) was 31.3% during summer and 45.3% during spring. The OCR of the nullipara heifers in the same herds was 59.2% in summer and 60.4% in spring. The OCR in summer was negatively correlated with the minimum temperature (r=-0.53), the relative humidity at 0800 hrs. (r=-0.47), and the relative humidity at 1400 hrs (r=-0.49), whereas the CRl during summer was negatively correlated only with the minimum temperature (r=-0.51). In 12 (13) feeding groups of cows examined in 6 herds, no correlation was found between rectal temperatures and the actual milk productions of the cows. In 14 (15) herds, the milk production in summer was lower than in spring; the decrease varied from 0.9%-18.2% (average 7.8%). A highly significant negative correlation was found between the OCR and the various parameters of protein intake: grams of crude protein/cow/day, grams of crude protein/kg FCM/day, and percentage of protein from total dry matter. Particularly high correlations were found between the OCR and the average amounts of protein/kg FCM/day in milk of all cows (r=-0.84).     

Clinical trial of chromium and yeast supplements on carbohydrate and lipid metabolism in diabetic men

Chromium (Cr) deficiency in experimental animals and in humans sustained by prolonged total parenteral nutrition has been shown to cause diabetes mellitus. Prior trials in humans indicated that Cr supplements, in either inorganic or organic form, may improve carbohydrate utilization. We report here a clinical double-blind, random cross-over trial of inorganic chromium trichloride, a brewer’s yeast that contained Cr as glucose-tolerance-factor (GTF), a brewer’s yeast extract without GTF, and a placebo. Forty-three outpatient diabetic men received three of these supplements for 4 months each. Subgroups included 21 ketosis-prone, 7 ketosis-resistant non-obese, and 15 ketosis-resistant obese men. Cr levels were followed pre- and post-treatment in hair, red blood cells, plasma, and urine. Response of carbohydrate metabolism to treatment was assessed in terms of change in insulin requirements, fasting plasma glucose, plasma cholesterol, and triglycerides, as well as the change in plasma glucose, glucagon, and insulin or C-peptide levels in response to a standard meal. In some men, these parameters were also measured after iv tolbutamide. Both the inorganic and organic oral Cr supplements increased measurable body pools of Cr in hair and red blood cells by about 25%. However, fasting plasma glucose and lipids and the glucose response to either the standard meal or to tolbutamide were not significantly altered by any of the treatments.     

Degradation of transplanted mitochondrial proteins by hepatocyte monolayers.

Reductively [3H]methylated rat mitochondria and mitochondrial-outer-membrane vesicles and mitochondrial-outer-membrane vesicles where monoamine oxidase is irreversibly labelled by [3H]pargyline have been transplanted into hepatocytes by poly(ethylene glycol)-mediated organelle or organelle-vesicle cell fusion. During subsequent culture of hepatocyte monolayers for 4-5 days, under conditions which mimic endogenous catabolic rates in vivo the transplanted organelle proteins retain their degradation characteristics observed in vivo (e.g. mitochondria: average t 1/2 72.5 h; monoamine oxidase: t1/2 55 h). In all cases protein degradation with first-order kinetics is only observed after an initial lag period (i.e. 24-30 h after fusion). Transplantation of fluorescein-conjugated organelles showed that the fluorescent material is rapidly internalized (average t1/2 1-6 h) and uniformly distributed in the cytoplasm. During a subsequent 18-24 h period (which corresponds to the lag period for intracellular destruction of transplanted mitochondrial material) the transplanted material is translocated to assume a perinuclear distribution. The destruction of transplanted mitochondrial proteins is compared with endogenous mitoribosomally synthesized proteins (average t1/2 52.5 h). Percoll fractionation of cell homogenates containing transplanted mitochondrial outer membranes where the enzyme monoamine oxidase is irreversibly labelled with [3H]pargyline shows a distribution of enzyme similar to lysosomal acid phosphatase. After transplantation of reductively methylated 3H-labelled mitochondrial-outer-membrane vesicles the cells were treated with leupeptin to alter lysosomal density. This treatment leads to the predominant association of acid phosphatase with dense structures, whereas the 3H-labelled transplanted material predominantly does not change density. Therefore transplanted mitochondrial-outer-membrane proteins are found in intracellular vesicular structures from which the proteins are donated for destruction, at least in part, by a lysosomal mechanism.     

Studies on dissimilatory sulfate-reducing bacteria that decompose fatty acids

Gliding motility, ultrastructure and nutrition of two newly isolated filamentous sulfate-reducing bacteria, strains 5ac10 and 4be13, were investigated. The filaments were always attached to surfaces. Growth was supported by addition of insoluble aluminium phosphate or agar as substrata for gliding movement. Electron microscopy of ultrathin sections revealed cell walls characteristic of Gramnegative bacteria; the undulated structure of the outer membrane may pertain to the translocation mechanism. Intracytoplasmic membranes were present. Acetate, higher fatty acids, succinate or fumarate served as electron donors and carbon sources. Strain 5ac10 grew also with lactate, but not with benzoate that was used only by strain 4be13. Strain 5ac10 was able to grow slowly on H₂ plus CO₂ or formate in the presence of sulfate without additional organic carbon source. The capacity of complete oxidation was shown by stoichiometric measurements with acetate plus sulfate. Both strains contained b- and c-type cytochromes. Desulfoviridin was detected only in strain 5ac10. The two filamentous gliding sulfate reducers are described as new species of a new genus, Desulfonema limicola and Desulfonema magnum.