Temporary infertility possibly associated with parenteral copper therapy in cattle.
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Animals↗
Biomedical subjects
D J Harris
Publications and source records attributed to D J Harris.
Contribution of cobalamin analogues to plasma vitamin B12 concentrations in cattle.
Plasma vitamin B12 concentrations in cattle were analysed by a radioisotope dilution assay using pig intrinsic factor and a microbiological assay using Euglena gracilis. Both assays provided similar results for samples of cattle plasma containing vitamin B12 concentrations ranging from 0.07 to 3.60 micrograms litre-1 (r = 0.95, P less than 0.001). The addition of excess cobinamide in the radioisotope dilution assay to block non-specific binding in the intrinsic factor preparation due to the presence of R-type binders, was used to determine the presence of cobalamin analogues. Cobalamin analogues accounted for up to 50 per cent of the total vitamin B12 concentration in samples of plasma from cows but were virtually undetectable in plasma from sheep.
Animal Feed↗
Soleus H reflex studies in humans at 40-70 bar in helium-oxygen-nitrogen (trimix).
Excitability of the Hoffmann (H) reflex was studied in 6 subjects at pressures of 40 to 70 bar during two trimix exposures (10% N2, 0.5 bar O2, the remainder He; Atlantis II and III simulated dives, Duke University Medical Center). In Atlantis II (12 h to 47 bar, 1 + 3 days to 66 bar), the H reflex recruitment ratio (Hmax/Mmax) was increased in 2 out of 3 subjects and reduced in the 3rd, while the usual facilitatory effect on the H reflex of a hand-grip reinforcement maneuver was reduced in all subjects. These results are similar to those previously seen in He-O2 dives and suggest a slight hyperreflexia mediated by an increase in alpha motoneuron excitability. In Atlantis III (1.5 days to 47 bar, 7 days to 66 bar) H recruitment ratios were normal in 2 subjects, and reduced in 1 subject (P less than 0.001). Early (III) and late (V) inhibitory phases of the H reflex recovery cycle were not significantly altered, while a 50-ms delay in the recovery cycle rebound (phase IV) in 5 out of 6 subjects at 66 bar (P less than 0.01) is attributed to the slowed muscle contraction. However, the increased amplitude of the rebound and the presence of clonic electromyographic potentials in Atlantis III are evidence of stretch receptor hyperexcitability that apparently persisted when H reflex excitability was normal. It is concluded that increased reflex responsiveness at depth is not promoted exclusively by either enhanced alpha motoneuron excitability or stretch receptor sensitivity but is mediated via both systems. Slower compression and the presence of N2 appear to preserve normal spinal inhibitory feedback and alpha motoneuron excitability but do not prevent increases in stretch receptor sensitivity.
Atmospheric Pressure↗
Mucolipidosis I.
A case of mucolipidosis I had clinical and histopathologic features that were a combination of changes found in both mucopolysaccharidoses and sphingolipidoses. Corneal clouding, spokelike cataracts, tortuous conjunctival and retinal vessels, and strabismus were clinical findings. Histopathologically, there were inclusion vacuoles similar to those seen in mucopolysaccharidoses; lamellar bodies typical of sphingolipidoses were rare. These vacuoles were seen in conjunctival and corneal epithelium and fibrocytes, conjunctival and retinal vessel endothelium, and all retinal cell layers.
Conjunctiva↗
Discordance for the Kleeblattschädel anomaly in monozygotic twins with thanatophoric dysplasia.
We describe monozygotic twins with thanatophoric dysplasia who were discordant for the Kleeblattschädel anomaly, but were identical in all other respects, including the histologic appearance of the endochondral growth plate. The observation suggests that the skull anomaly represents a variable manifestation of thanatophoric dysplasia, and that its occurrence in an infant with this bone dysplasia should not alter the low recurrence risk generally given.
Diseases in Twins↗
Factors predisposing dairy and beef cows to grass tetany.
In a study of dairy and beef herds on 120 farms in south-western Victoria, losses attributed to grass tetany were shown to have been an important cause of economic loss during the cooler months of 1980. Thin dairy cows had a higher incidence of suspected grass tetany than dairy cows in moderate body condition, and both thin and fat beef cows had a higher incidence than beef cows in moderate body condition. A lower incidence was found among dairy cows when the available pasture or hay contained a high percentage of clover, when cows in moderate body condition had been grazed on pastures topdressed with low rates of potassium fertilisers, and when cows had been rotated onto fresh pasture at least daily rather than at 2 or 3 day intervals. The incidence among dairy cows was also associated with the length of available pasture, the correlation being positive for cows of moderate body condition, but negative for thin cows. Possible reasons for the associations are discussed. Only a small proportion of farmers adopted measures to prevent grass tetany, and those who did often applied them inefficiently. Practicable control measures are suggested on the basis of the survey results.
Age Factors↗
Liquid ventilation in dogs: an apparatus for normobaric and hyperbaric studies.
A liquid-breathing apparatus is described for remote surface studies and for use in experiments of near-hydraulic compression in dogs. It consists of a flexible tank sealed against chamber gas, containing a supply of clean warmed (38 degrees C) fluorocarbon (FC-80) equilibrated with 1 bar O2 and an electronically controlled means of delivering the liquid to the dog. Each breath (tidal volume 290 ml) was "weighed" into the animal by the signal from a force platform supporting the dog and a digital control unit that automatically actuated inspired-and expired-line solenoid valves. The apparatus was successfully used to remotely maintain liquid ventilation in awake dogs for 2 h during surface studies (5 dogs) and in dives to 1,000 m seawater (5 dogs). During liquid breathing, mean arterial O2 partial pressure was always adequate (congruent to 300 Torr) and mean arterial CO2 partial pressure was normal (less than or equal to 40 Torr). An uncompensated metabolic acidosis was indicated by low pH values and a decrease in arterial base excess to--4.5 meq x 1(-1). O2 uptake and CO2 output appeared to be significantly lower (42 and 35%, respectively) during liquid ventilation.
Animals↗
Force and duration of muscle twitch contractions in humans at pressures up to 70 bar.
The contraction peak force (CPF) and contraction time (CT) of the soleus Hoffmann (H) reflex and motor (M) response muscle twitch were measured in three subjects during the 686-m seawater Atlantis III simulated dive at Duke University. The mean CPF of both H and M twitches was observed to be 40-60% larger during compression than in predive control studies (P less than 0.001 for M response). This effect was sustained during the first 300 m of decompression, while postdive values were normal. Rate of contraction, as measured by changes in CT, was slowed significantly but only during compression (by 23% in the H reflex at 66.4 bar, P less than 0.001). These marked effects in CPF and CT cannot be explained by the small increases observed in the muscle action potential latency and duration, or other neuronal mechanisms. It is concluded that the twitch contraction of skeletal muscle is significantly slowed and augmented at pressure due to changes in excitation-contraction coupling or in the contractile process itself. These findings may be of importance in interpreting the etiology of many neuromuscular signs of the high-pressure neurological syndrome.
Atmosphere Exposure Chambers↗
Latency changes in the human somatosensory evoked potential at extreme depths.
Somatosensory evoked potentials to lower limb stimulation were recorded from the three participants in a recent chamber dive to a world depth record of 686 m (2250 ft). Because of the 10% nitrogen breathing mixture, both inert gas narcosis and high pressure nervous syndrome were factors in the dive. Latencies of evoked potential peaks were measured relative to the peak of the first cortical component, P1, in order to separate central from peripheral effects. Several peak latencies changed systematically during compression. The several components of the somatosensory evoked potential appeared differentially sensitive to either inert gas narcosis or the high pressure nervous syndrome with increasing depth. The latencies of all peaks following the initial cortical P1 were shorter at depth than in surface control recording. This is consistent with a state of hyperexcitability in the brain that is felt to characterize the high pressure nervous syndrome. Changes in peak latency were consistent across subjects and in some cases achieved statistical significance despite the small number of subjects available for testing. Although these findings are preliminary, they suggest that evoked potential latencies may have value as a means of following the effects of extreme pressure on the central nervous system.
Atmosphere Exposure Chambers↗
Corneal keloid in Lowe's syndrome.
Bilateral corneal keloids in a boy wih Lowe's syndrome were examined by conventional light and electron microscopy. There were no signs of perforating corneal trauma or iridocorneal incarceration in either eye. The corneal keloids consisted of haphazardly arranged bundles of collagen fibers, fibroblasts, and fenestrated blood vessels. The anterior region of the keloids showed signs of active progression and epithelial epidermalization. The etiology of keloids in Lowe's syndrome remains obscure. Considerations include excessive local delivery of amino acids and unknown noxious substances through the leak corneal vessels, seepage of similar substances across the defective blood-aqueous barrier and the decompensated endothelium, repeated external trauma with associated inflammation, phenytoin (Dilantin) therapy, and congenital predisposition. No data are available on the management of the progressive course of corneal keloids. Possible empirical regimens include local excision, pressure therapy, topical corticosteroids, and cromolyn sodium.
Child↗
Congenital ptosis. Results of treatment using lyophilized fascia lata for frontalis suspensions.
In a prospective collaborative study, congenital ptosis was repaired using lyophilized allogeneic fascia lata as the suspension material for frontalis sling procedures. Over 50 cases of unilateral and bilateral ptosis procedures were performed by pediatric ophthalmologists during the initial study period. No infections or evidence of tissue rejection were reported during a follow-up period of up to 24 months. Four failures, ascribed to slippage, were noted within the first several months and required regrafting. In an additional case, minimal slippage occurred, but resulted in satisfactory lid levels. All remaining cases achieved satisfactory cosmetic and functional results. Most collaborators found this form of preserved fascia lata to be superior to nylon polyfilament, cable-type suture. Clinical features of the patient population included a high incidence of strabismus (28%) and amblyopia (24%).
Adolescent↗
Parental trisomy 21 mosaicism.
A family with three children with trisomy 21 in which the mother is a phenotypically normal, trisomy 21/normal mosaic was studied. Chromosome 21 fluorescent heteromorphisms were used to document that two of the three number 21's in two of the Down syndrome offspring were of maternal origin. Five cytogenetic surveys in which both parents of a child with trisomy 21 were studied have been reviewed. From these data, it is estimated that 3% of couples producing a child with trisomy 21 can be explained by parental mosaicism. From 17 informative sibships, with one parent mosaic, the segregation ratio was estimated to be 0.43 +/- 0.11.
Adult↗
Propionic acidemia: a clinical update.
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Amino Acid Metabolism, Inborn Errors↗
Factors predisposing to parturient paresis.
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Age Factors↗