Search PubMed⌕ Search

Biomedical subjects

R A Irving

Publications and source records attributed to R A Irving.

31 records · Page 2Linked to original sources
PubMed1988

Crystalluria in marathon runners. II. Ultra-marathon--males and females.

Particle-volume size distribution curves for the urines of a group of male ultra-marathon runners have been recorded and show the same features as those reported in an earlier study involving standard marathon runners. It is again suggested that these features indicate risk of urinary stone formation although this does not appear to be increased by the more stressful ultra-marathon. Distribution curves obtained for female runners closely resemble those recorded for controls, thus rendering it impossible to assess their risk profile. A commonly observed feature of both the male and female urines was the presence of various urinary salts. Profuse calcium oxalate dihydrate crystals were detected in some samples 11 days after the race. It is suggested that entrapment sites within the urinary tract have a selective specificity for these crystals while urinary salts pass through unhindered.

Adult↗
PubMed1986

Crystalluria in marathon runners. 1. Standard marathon--males.

Epidemiological evidence suggests that marathon runners have a higher incidence of renal stone formation than occurs in the general population. Since crystalluria and stone disease are thought to be related, we subjected urine samples from a group of marathon runners to particle counting and sizing in a Coulter Counter equipped with a population accessory unit. The volume-size distribution curves so obtained were bimodal with one peak occurring in the 2-5 micron diameter range and a second in the 15-32 micron diameter range - a pattern that is remarkably similar to the distributions reported for recurrent idiopathic stone formers and distinctly different to those recorded for control subjects. Analyses by scanning electron microscopy and X-ray powder diffraction revealed other features which are regarded as typical of stone formers' crystalluria. These physicochemical data indicate that marathon runners may be at increased risk of urinary stone formation.

Adult↗
PubMed1986

The immediate and delayed effects of marathon running on renal function.

Daily blood and 24-hour urine samples from 6 runners were studied for 2 days before and for 5 days after a 42.2 km. marathon footrace run in cool environmental conditions. Although the race caused muscle damage as shown by the increased post-race serum creatine kinase activity and C-reactive protein levels, renal function measured by urine flow rates, creatinine clearance and protein excretion was normal during the race. Sodium and fractional sodium excretion decreased during the race despite a maintained osmolar clearance, and remained low for the next 48 hours, whereas osmolar clearance decreased sharply for the remainder of the race day but it was significantly elevated on days 2 to 4 after the race. Creatinine clearance was increased significantly 24 hours after the race, and reached its peak 3 days after the race, while urine flow rates were elevated from days 2 to 5 after the race. Urea excretion was significantly decreased 3 to 5 days after the race, while creatinine excretion was increased significantly on day 3 after the race. Glomerular proteinuria occurred 24 hours after the race with no associated reduction in tubular reabsorption of the low molecular weight protein beta-2-microglobulin. This study shows previously unrecognized substantial delayed effects of prolonged exercise on renal function. The nature of these changes may reflect catabolic followed by anabolic processes in muscle as well as changes consequent on excess sodium retention and related fluid compartment shifts.

Adult↗
PubMed1986

Struvite crystalluria and urolithiasis in cross Labradors.

Recurrent struvite crystalluria and urolithiasis in a cross-Labrador bitch was studied using a combined Coulter-Counter and scanning electron microscope (SEM) approach. Staphylococcus bacteria were cultured from the patient's urine as well as from the calculi themselves. Urine samples were subjected to particle counting and sizing during active and non-active periods of stone formation. Size distribution curves so obtained were identical as were those derived from sterile and non-sterile specimens. These showed a peak incidence at a diameter of 5 microns. Particle sizes for 6 controls were also determined and showed an even distribution over a much wider range with small peaks occurring at 3, 10, and 20 microns diameters. SEM studies of urine sediments revealed the presence of struvite crystals in all the controls as well as in the stone-former. These occurred in a variety of shapes and sizes but were generally larger in the controls. SEM also revealed intimate admixtures of struvite and apatite in calculi surgically removed from the patient. The results of this study indicate that crystal numbers are of greater significance than crystal size. It is also suggested that Cross-Labradors may be unusually predisposed to struvite crystalluria. The repeated recurrence of struvite urolithiasis in the subject indicates a possible inherent physiological malfunction in the animal's ability to cope with this crystalluria. The absence of a nucleation inhibitor in the stone-former's urine is also postulated.

Animals↗
PubMed1985

Physiological and biochemical measurements during a 4-day surf-ski marathon.

We studied competitors in the 1983 Texan Challenge surf-ski paddle marathon to determine the effects of 4 days prolonged paddling on sweat rates, rectal temperatures, renal function, serum glucose, free fatty acid, porphyrin and C-reactive protein levels and serum creatine kinase activity. Sweat rates during the race varied from 0.5 to 1.0 l/h, and peak rectal temperatures did not exceed 38 degrees C, even in the most dehydrated subjects. Renal function was unchanged during the race. Plasma renin activity remained low during the race but C-reactive protein levels and serum creatine kinase activity were elevated. Seventy per cent of the subjects had immediate post-exercise blood glucose levels below 3.9 mmol/l after the 1st and 4th days, and 27% had values below 3.0 mmol/l, one competitor requiring intravenous glucose therapy on the beach. Surf-ski paddling is therefore associated with low sweat rates, low levels of dehydration, low body temperature and unchanged renal function. The low post-exercise blood glucose levels indicate that competitors must eat high-carbohydrate diets for the duration of the event and must either eat carbohydrate-containing foods or drink concentrated carbohydrate solutions while paddling.

Blood Glucose↗
PubMed1983

Viral membrane glycoproteins: comparison of the amino terminal amino acid sequences of the precursor and mature glycoproteins of three serotypes of vesicular stomatitis virus.

The NH2-terminal amino acid sequences of the envelope glycoproteins and the in vitro synthesized, nonglycosylated precursors of the glycoproteins of three serotypes, namely Indiana (Toronto), Cocal, and New Jersey (Concan) of vesicular stomatitis virus were determined. A comparison of the sequences showed little homology in the signal peptides present in the nonglycosylated precursors except for their high hydrophobic amino acid content. In contrast, the NH2-terminal amino acid sequences of the mature envelope glycoproteins revealed extensive homology suggesting that this region is conserved and may be involved in essential biological function(s) of the rhabdovirus.

Amino Acid Sequence↗
PubMed1982

Shedding of vesicular stomatitis virus soluble glycoprotein by removal of carboxy-terminal peptide.

A comparison of partial NH2-terminal sequences of vesicular stomatitis viral glycoprotein G (molecular weight, 69,000) and the soluble extracellular glycoprotein antigen Gs (molecular weight, 57,000) shows that both of the sequences are identical. Tryptic fingerprint analyses show that Gs lacks the carboxy-terminal region containing the membrane-anchoring hydrophobic domain of G. These results suggest that Gs is formed by cleavage in the carboxy-terminal region of G.

Amino Acid Sequence↗
PubMed1979

Synthesis and assembly of membrane glycoproteins: presence of leader peptide in nonglycosylated precursor of membrane glycoprotein of vesicular stomatitis virus.

Translation of mRNA encoding vesicular stomatitis virus envelope glycoprotein G by as membrane-free ribosomal extract obtained from HeLa cells yielded a nonglycosylated protein (G1 (Mr 63,000). In the presence of added microsomal membranes, G1 was converted to the glycosylated protein (G2 (Mr 67,000) which is inserted in the membrane vesicles as a transmembrane protein. Labeling with methionine donated by wheat germ initiator tRNA1Met showed that G1 but not G2 contains methionine in the NH2-terminal position. Determination of the NH2-terminal sequence of G1, G2, and G showed that a leader peptide of 16 amino acids is present in G1 but absent from the glycosylated proteins G2 and G. This leader peptide contains at least 62% hydrophobic amino acids and is removed presumably during insertion of G1 into the membrane.

Amino Acid Sequence↗
PubMed1974

Specific changes in the messenger ribonucleic acid content of the rat ventral prostate gland after androgenic stimulation. Evidence from the synthesis of aldolase messenger ribonucleic acid.

1. Aldolase was selected as a suitable marker for following the androgenic regulation of mRNA synthesis in the prostate gland. 2. Antibodies raised in rabbits against crystalline prostate aldolase were used to monitor the synthesis of this androgen-induced enzyme after hormonal stimulation of castrated animals, by using procedures in vivo and in vitro for the translation of prostate poly(A)-rich mRNA. 3. After androgenic stimulation in vivo the poly(A)-rich mRNA was isolated from the prostate gland and other tissues of castrated rats, and added to a protein-synthesizing system in vitro derived from Krebs II ascites-tumour cells. By using this approach it was found that androgens regulate the synthesis of aldolase mRNA in a highly tissue-specific manner. Stimulation of aldolase mRNA synthesis reached a maximum after 8h of androgenic treatment and then declined. 4. The androgenic control of aldolase mRNA synthesis was also investigated in vivo. After treatment of castrated animals with various steroids in vivo [(35)S]methionine was injected directly into the prostate gland, and labelled aldolase was selectively precipitated from isolated polyribosomes with anti-aldolase serum. The regulation of aldolase mRNA synthesis in the prostate gland was stringently steroid-specific and could only be evoked by androgens. After a single injection of testosterone, aldolase synthesis reached a maximum after 16h of hormonal stimulation and then declined. 5. Although androgens exert significant control over transcriptional processes in the prostate gland, and appear to regulate the synthesis of aldolase mRNA de novo, the possibility exists for additional means of control at the translational level of aldolase synthesis. The results are discussed in the context of the overall mechanism of action of androgens.

Androgens↗