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Biomedical subjects

R H Douglas

Publications and source records attributed to R H Douglas.

At least 55 records · Page 3Linked to original sources
PubMed1987

Changes in thecal and granulosa cell LH and FSH receptor content associated with follicular fluid and peripheral plasma gonadotrophin and steroid hormone concentrations in preovulatory follicles of mares.

Individual antral follicles from 11 horse mares were studied at three stages of the oestrous cycle to determine the characteristics of the presumptive ovulatory follicle. Mares were ovariectomized (ovex) during the late luteal phase on Day 14 after ovulation (Group 1) and on the 1st (Group 2) or 4th (Group 3) day of oestrus. Every follicle greater than 5 mm in diameter was dissected from each ovary; follicles greater than or equal to 15 mm in diameter were analysed separately while others were pooled by size for subsequent analyses. The presumptive ovulatory follicle possessed the following characteristics: in Groups 2 and 3 they were the largest in size; in all groups they contained the largest amount of protein in the granulosa cell component; they were the most vascular; they contained the highest follicular fluid oestradiol concentration; and they possessed the highest granulosa cell LH/hCG receptor content. In 9 mares, there was one such follicle present. In 2 mares, there were 2 such follicles present and one of these mares had a history of repeated double ovulations. The presumptive ovulatory follicle of Group 1 mares contained more thecal LH receptor than did non-ovulatory follicles. There were no differences in granulosa FSH receptor content amongst follicles, although smaller follicles tended to have increased FSH receptor content. Follicular fluid FSH and LH reflected peripheral hormone concentrations with follicular fluid LH being highest in presumptive ovulatory follicles of Group 3 mares. Follicular fluid progesterone concentrations tended to be higher in presumptive ovulatory follicles when compared with small follicles. Within a class of follicle, follicular fluid androstenedione and testosterone concentrations were lower in follicles of Group 1 mares than in follicles from Group 2 and 3 mares, reflecting endogenous stimulation of androgen biosynthesis by LH. Elevated follicular-fluid oestradiol occurred only in the presumptive ovulatory follicle with concentrations at least 30-50-fold higher than in non-ovulatory follicles. These results demonstrate that the presumptive ovulatory follicle in horse mares has been selected by at least Day 14 after ovulation and can be identified at this time by its various biochemical characteristics. Only after the first day of oestrus were physical characteristics such as size accurately able to predict ovulatory follicle status. These results clearly demonstrate the relationship between LH stimulation of androgen biosynthesis in vivo regardless of follicle size or status (ovulatory or non-ovulatory).(ABSTRACT TRUNCATED AT 400 WORDS)

Androstenedione↗
PubMed1986

Photopic spectral sensitivity of a teleost fish, the roach (Rutilus rutilus), with special reference to its ultraviolet sensitivity.

This study reports photopic spectral sensitivity curves (351-709 nm) for four individual roach, Rutilus rutilus, determined by two choice appetitive training. All four curves show four sensitivity maxima at 361-398 nm, 421-448 nm, 501-544 nm and 634-666 nm which are related to the four known roach photopic visual pigments (Avery et al. 1982). The overall shape of the curves at long wavelengths indicates inhibitory interactions between the red and green cone mechanisms. That the high behavioural sensitivity in the UV is caused by a specific ultraviolet visual pigment and is not due to aberrant stimulation of the other cone types is shown by the redetermination of spectral sensitivity at short wavelengths (351-501 nM) following the selective bleaching of the three longer wavelength visual pigments. This depresses the blue sensitivity to a greater degree than the relatively unaffected UV sensitivity maximum. Spectral transmission data from two corneas and four lenses show that they transmit considerable amounts of light in the near UV.

Adaptation, Physiological↗
PubMed1986

A description of a low field resistive magnetic resonance imaging system and its application in imaging midline central nervous system pathology.

A commercial low field magnetic resonance imaging (MRI) system installed in the Royal Infirmary, Edinburgh at the end of 1983 has since been used for the clinical investigation of over 1000 patients. This system uses an interlaced saturation recovery and inversion recovery pulse sequence which yields four types of clinical image. AT1 weighted image has been found to be the most sensitive for the detection of pathology. Several examples of pathology with negative X-ray computed tomography examinations including three examples of a syrinx and two cases of tonsillar herniation have been demonstrated using this system. It is suggested that the system could provide a routine clinical service for imaging the central nervous system.

Brain↗
PubMed1986

Correlation of human NMR T1 values measured in vivo and brain water content.

A relationship has been demonstrated between nuclear magnetic resonance (NMR) longitudinal relaxation times (T1 values) obtained in vivo in both normal and oedematous (peritumoral) brain tissue, and measurements of brain water obtained by gravimetric analysis of operative samples. Significant correlations were found in seven patients in both cortex (r = 0.97, P less than 0.001) and white matter (r = 0.92, P less than 0.001). These findings suggest that NMR may prove a useful technique for monitoring brain oedema.

Body Water↗
PubMed1985

Characterisation of acute myocardial infarction by gated magnetic resonance imaging.

In studies with gated nuclear magnetic resonance imaging, patients with recent transmural myocardial infarction showed significantly longer spin-lattice relaxation times (T1) in the infarct area than did healthy volunteers or patients with non-ischaemic or chronic ischaemic heart disease. 10 of the 13 patients had a T1 longer than that found in any healthy subject or in any patient with other heart disease. Changes in T1 should prove useful in the assessment of interventions designed to limit infarct size.

Adult↗
PubMed1985

Nuclear magnetic resonance in hypertrophic cardiomyopathy.

The large differences in the spin lattice relaxation times (T1) of blood and myocardium (measured by nuclear magnetic resonance) allow the heart to be visualised without the use of contrast media. The findings using nuclear magnetic resonance in 11 unselected patients with hypertrophic cardiomyopathy were compared with those in equal numbers of normal subjects and patients with electrocardiographic features of left ventricular hypertrophy. In patients with hypertrophic cardiomyopathy characteristic septal hypertrophy was noted together with variable and sometimes pronounced hypertrophy of the left ventricular free wall, which is consistent with the heterogeneous nature of this disease. The mean (SD) ratio of septal to free wall thickness was 1.5(0.8) for patients with hypertrophic cardiomyopathy, 0.8(0.2) for those with left ventricular hypertrophy, and 0.9(0.2) for normal subjects. Although septal measurements by nuclear magnetic resonance were greater than those obtained by echocardiography there was a significant correlation between the two. Septal and free wall area were significantly smaller in normal subjects. There were no differences in septal or free wall T1 values between the three groups. Non-gated nuclear magnetic resonance can detect septal and free wall hypertrophy. With the addition of multiple slice acquisition, rapid estimation of myocardial mass will be possible allowing the potentially important assessment of progression or regression of myocardial hypertrophy.

Adult↗
PubMed1984

The installation of a commercial resistive NMR imager.

It has been demonstrated that a relatively low-cost resistive NMR imager can be installed in a normal hospital environment without many major or expensive modifications. The magnet can be adjusted to give adequate uniformity and there is sufficient RF shielding to give good quality clinical images (Fig. 3). The fringe field of the magnet of this system, which operates at the lowest field strength of any commercial NMR imager, does not present a problem to imaging unit staff (NRPB, 1984). The long term reliability and detailed specifications with regard to image quality have yet to be determined. These will be determined whilst the imager is being used for clinical studies as part of the national clinical evaluation of NMR imaging supported by the Medical Research Council.

Hospital Departments↗
PubMed1983

Endogenous control of spinule formation in horizontal cells of the teleost retina.

The process of horizontal cells invaginating teleost cone pedicles are studded with small finger-like projections which are present only in the light-adapted state. The aim of this study was to investigate whether the formation and degradation of these so-called spinules, which are thought to function as feed-back synapses onto the cones, is endogenously controlled. Three types of experiment were carried out involving fish entrained to a 12 h light/dark cycle: 1) The number of spinules was determined in goldfish at various times during exposure to either constant darkness (36 h) or constant light (57 h). 2) The time course of spinule formation and degradation in goldfish was investigated following exposure to light or darkness at various times during the light/dark cycle. 3) The time course of flash-induced spinule formation in tench following dark adaptation at noon was compared to that following dark adaptation at midnight. The results of these experiments show that spinule formation and degradation are partially under endogenous control but that they need light and full expression. This endogenous rhythm is reflected in the time courses of spinule formation and breakdown during different phases of the light/dark cycle.

Adaptation, Physiological↗
PubMed1983

Spectral sensitivity of rainbow trout (Salmo gairdneri).

The photopic spectral sensitivity of the rainbow trout, Salmo gairdneri, was determined using a two choice appetitive training method. The resulting curve had three maxima at around 391-473, 490-573 and 650-669 nm. Maximum sensitivity was reached with short wavelength stimuli. Thresholds for white light were also obtained. The results show that the rainbow trout has an action spectrum that is similar to that of other fresh water teleosts in similar circumstances, and that it most likely has the ability to distinguish monochromatic stimuli on the basis of wavelength. Using thresholds to white light and typical freshwater visual pigments, the form of the spectral sensitivity curve was found to be best fitted by independent receptor action at the short wavelengths and by inhibitory interaction between the green and red receptors at the longer wavelengths.

Animals↗
PubMed1983

Morphologic changes in teleost primary and secondary retinal cells following brief exposure to light.

Light adaptive morphologic changes in the teleost retina, such as movements of rods, cones, and epithelial pigment and spinule formation on horizontal cell terminals, are normally associated with continual exposure to light. Depending on a variety of factors these processes are generally completed within 30-60 min. In this report we show that a brief exposure to light (1-2 min) preceded and followed by darkness is sufficient to elicit these changes in four species of teleost; the trout (Salmo gairdneri), the tench (Tinca tinca), the carp (Cyprinus carpio), and the goldfish (Carassius auratus). A brief pulse is as effective in causing cone migration and an increase in the number of spinules as continual exposure; however, it is sometimes less effective in causing pigment migration. The photomechanical changes following a brief period of light are always completed more quickly and show greater species variability than the formation of spinules. These results show that the various morphologic manifestations of light adaptation are autonomous processes that need only a short pulse of light to trigger the whole sequence of events. This is of interest when considering their control mechanisms and may have consequences for physiologic work involving experiments on dark-adapted eyes.

Adaptation, Physiological↗
PubMed1982

Purification of an alpha-N-acetylglucosaminyltransferase from the yeast Kluyveromyces lactis and a study of mutants defective in this enzyme activity.

An enzyme activity in Kluyveromyces lactis that catalyzes the transfer of N-acetylglucosamine from uridine diphosphate N-acetylglucosamine to alpha Man(1 leads to 3) alpha Man ( 1 leads to 2) alpha Man (1 leads to 2)Man to yield alpha Man(1 leads to 3) [alpha GlcNAc(1 leads to 2)] alpha Man(1 leads to 2) alpha Man (1 leads to 2)Man, a mannoprotein side-chain unit, has been solubilized by Triton X-100 and purified 18000-fold by a combination of ion-exchange chromatography, gel filtration, hydrophobic chromatography, and adsorption to a lectin column. The enzyme activity from a K. lactis mutant (mnn2-2) that made mannoprotein lacking N-acetylglucosamine in its side chains, but that possessed a normal level of transferase activity in cell extracts, was purified and compared with the enzyme from the wild-type strain. Both transferase activities are integral membrane proteins found in particles associated with endoplasmic reticulum. The two purified enzymes had the same apparent size, heat stability, Mn2+ requirement, and Km for donor and acceptor and a similar Vmax. Wild-type and mutant cells had similar pool sizes of sugar nucleotide donor, and they incorporated labeled N-acetylglucosamine into chitin at similar rates. No evidence was obtained for an inactive enzyme precursor in mutant cells that was activated upon breaking the cells, nor did the mutant cells contain a transferase inhibitor or a hexosaminidase that could remove the sugar from the mannoprotein during processing and secretion. The mnn2-2 locus appears to be allelic with a second mutant, mnn2-1, that has the same phenotype but that lacks transferase activity in cell extracts. This suggests that the two mutations affect the structural gene for the transferase, and we conclude that the mnn2-2 mutant could contain an altered enzyme that fails to function because it is improperly localized or oriented in the membrane.

Acetylglucosamine↗
PubMed1982

Endogenous patterns of photomechanical movements in teleosts and their relation to activity rhythms.

The retinal rods, cones and epithelial pigment of most lower vertebrates display rhythmic photomechanical (retinomotor) migrations in response to changes in ambient lighting conditions. This study examines the extent of these migrations in the absence of the daily changes in illumination (constant darkness and constant light) in three species of teleosts. Salmo trutta, a crepuscularly active fish, showed two peaks of light adaptation occurring around dawn and dusk when kept in constant darkness. Tinca tinca, a nocturnal species, also showed an endogenous rhythm during extended periods of darkness, but, unlike Salmo trutta, it was light-adapted throughout what would normally have been "day". At the maximal extent of migration under conditions of continual darkness, the pigment migrated 59% as much as it did during a normal light/dark cycle. Nannacara anomala, a tropical diurnally active species, showed a similar but more pronounced rhythm than Tinca tinca for all 3 days of experimental darkness, behaving essentially identically to fish exposed to a light/dark cycle. Nannacara anomala also displayed a weak rhythm when kept in constant light. It is concluded from these and previous results that the pattern of endogenous photomechanical movement depends both on the activity pattern of a species and on the constancy of the lighting conditions to which it has been exposed during its lifetime.

Animals↗
PubMed1982

Twinning in mares: A survey of veterinarians and analyses of theriogenology records.

Responses of 22 veterinarians to a questionnaire and the records of three brood-mare farms were examined to obtain information on twinning. The incidence rates of multiple ovulations on the three farms were 9%, 11%, and 22%. The multiple ovulation rate was reduced 42-67% in foaling mares compared to barren and maiden mares. Multiple ovulations were significantly more frequent in Thoroughbreds (19%) than in Quarter Horses (9%) and Appaloosas (8%). Both the questionnaire and the farm records indicated a high degree of repeatability of multiple ovulations and twin pregnancies within mares and within certain family lines. The likelihood of multiple ovulations was approximately doubled when the preceding cycle also had multiple ovulations. On two of the farms, breeding was withheld or postponed until after the first ovulation when multiple follicles were present. There were no significant differences in overall reproductive efficiency (pregnancy and foaling rates) among the three farms and the incidence of observed twin abortions or births was low on all three farms (0.4, 0.2, and 0%, respectively).

Journal Article↗
PubMed1982

The outcome of twin pregnancies in mares.

Brood-farm veterinarians were surveyed and theriogenology records were examined to obtain information on the natural outcome of rectally-diagnosed twin pregnancies. Four of the veterinarians estimated that 50% of mares with twin embryos had single foals. In the analyses of palpation records, 31 53 (58%) of the diagnosed twin pregnancies terminated in birth of one foal. However, the loss of one embryo without the loss of the other occurred significantly more often before day 40-42 (30 53 ; 57%) than after day 40-42 (1 16 ; 6%). Of the remaining 15 mares with diagnosed twins at day 40-42, 5 had two foals and 10 had no foals. The methods used for intervention when twins were diagnosed were unsatisfactory. Complete termination of pregnancy with a prostaglandin or an intrauterine flushing resulted in failure to reestablish a singleton pregnancy during the operational breeding season in 10 11 mares. Attempts to eliminate one embryo resulted in loss of both in 6 7 mares. The results indicated that, at the present time, nonintervention should be given more consideration as a method of handling twin pregnancies.

Journal Article↗
PubMed1982

The use of radioreceptor assay for the detection of pregnancy in the mare.

Jugular blood samples were collected between 42-45 days from the last breeding for measurement of pregnant mare serum gonadotropin (PMSG) and progesterone in 46 pregnant mares. A radioreceptor assay (RRA) was developed to measure human chorionic gonadotropin (hCG) and subsequently modified to measure PMSG. Highly purified hCG was iodinated using a lactoperoxidase enzymatic procedure and served as the labeled antigen for both the hCG and PMSG RRA. Standard curves were generated using purified hCG or PMSG. Bovine corpora lutea served as the receptor source. The assay was conducted at 37 degrees C for one hour with a total elapsed time from preparation of the luteal cell homogenate until final results were calculated of 2.5 hours. Twelve of the 46 mares failed to maintain their pregnancy, returned to estrus and reovulated after 45 days post-breeding (non-foaling mares). Thirty-four of the 46 mares delivered foals following a gestation of normal length. Mean concentrations of PMSG in the foaling mares was higher than in non-foaling mares. A concentration of 6.9 I.U. of PMSG/ml was used as the lowest concentration necessary for the confirmation of pregnancy. Five of the mares delivering foals had low concentrations of PMSG and were called non-pregnant. Thus, the incidence of false negatives by RRA was 14.7%. All of the non-foaling mares were correctly diagnosed non-pregnant for an error rate (false positive) of 0.0. Mare Immunological Pregnancy (MIP) tests on the 12 non-foaling mares indicated three false positives - an error rate of 25%. Of the 34 foaling mares, the MIP test indicated 8 inconclusive or false negatives, an error rate of 23.5%. At day 42-45, there was no significant difference in progesterone concentrations (determined by RIA) between foaling and non-foaling mares. RRA is a quick, accurate and quantitative method for measuring PMSG in the mare and can be used to diagnose pregnancy at 42-45 days post-ovulation. Plasma progesterone concentrations at this time were not associated with subsequent pregnancy maintenance as were plasma PMSG concentrations.

Journal Article↗