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Biomedical subjects

J R Thompson

Publications and source records attributed to J R Thompson.

At least 73 records · Page 4Linked to original sources
PubMed2000

Skeletal and cardiac muscle protein turnover during cold acclimation in young rats.

The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5 degrees C (cold) or 25 degrees C (control). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. Protein mass by day 20 was approximately 28% lower in skeletal muscle (gastrocnemius and soleus) and approximately 24% higher in heart in cold compared with control rats (P < 0.05). In skeletal muscle, the fractional rates of protein synthesis (k(syn)) and degradation (k(deg)) were not significantly different between cold and control rats, although k(syn) was lower (approximately -26%) in cold rats on day 5; consequent to the lower protein mass, the absolute rates of protein synthesis (approximately -21%; P < 0. 05) and degradation (approximately -13%; P < 0.1) were lower in cold compared with control rats. In heart, overall, k(syn) (approximately +12%; P < 0.1) and k(deg) (approximately +22%; P < 0.05) were higher in cold compared with control rats; consequently, the absolute rates of synthesis (approximately +44%) and degradation (approximately +54%) were higher in cold compared with control rats (P < 0.05). Plasma triiodothyronine concentration was higher (P < 0.05) in cold compared with control rats. These data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover. In heart, unlike skeletal muscle, rates of protein turnover did not appear to immediately return to normal as increased rates of protein turnover were observed beyond day 5. These data also indicate that increased rates of protein turnover in skeletal muscle are unlikely to contribute to increased metabolic heat production during cold acclimation.

Acclimatization↗
PubMed2000

Effect of maternal smoking on ventilatory responses to changes in inspired oxygen levels in infants.

Maternal smoking is a major independent risk factor for sudden infant death syndrome (SIDS). Respiratory control deficits have been implicated in SIDS. The aim of this study was to test the hypothesis that infants born to smoking mothers have reduced ventilatory responses to changes in inspired oxygen. Smoking and nonsmoking women were recruited in midpregnancy and smoking status confirmed by measurement of urinary cotinine. To control for confounding factors of smoking each mother-infant pair in the smoking group was matched to a pair in the nonsmoking group for social class, maternal age and parity, feeding, birthweight, gestational age, and infant sex. Infants were seen overnight at approximately 10 wk of age for tests of respiratory control, using the alternating breath test. Ventilation was measured by respiratory inductance plethysmography and inspired and end-tidal oxygen levels were determined by mass spectrometry. Data were obtained from 40 infants (17 in the smoking group). Responses were similar in both groups for 10 respiratory parameters including respiratory drive and timing, and there were no significant differences. The mean end-tidal oxygen level when 40% O(2) was delivered was an average of 1.13% higher in the smoking group (p = 0.0067), although the inspired oxygen levels were not different. In conclusion, we did not find an independent effect of maternal smoking on respiratory control. The differences in end-tidal oxygen levels during the alternating breath test may represent differences in alveolar ventilation.

Female↗
PubMed2000

Effects of inbreeding on production and survival in Holsteins.

Responses of registered Holstein cows to various levels of inbreeding were examined with pedigree data supplied by the Holstein Association USA and test-day production data from 1970 through 1998 obtained from the Animal Breeding Center at Cornell University. Rate of increase in level of inbreeding has been accelerating over time, making it more difficult for producers to make matings that avoid the potentially deleterious effects of inbreeding. Milk production losses per lactation caused by inbreeding were generally 35 kg per percentage inbreeding level >0.01 but increased to 55 kg per percentage inbreeding level from 0.07 to 0.10. Somatic cell score was not affected by level of inbreeding. Inbreeding had the greatest effect on production at ages <22 mo and early in lactation. Early onset of the deleterious effects of inbreeding resulted in larger net present value losses than when effects of inbreeding occurred later. Losses were likely enhanced due to the need to freshen animals as early as possible to maximize net present value returns. Survival decreased as level of inbreeding increased and was likely to have a greater negative impact on the financial health of the dairy enterprise than production losses.

Age Factors↗
PubMed2000

Effects of inbreeding on production and survival in Jerseys.

Responses of registered Jersey cows to various levels of inbreeding were examined with pedigree data supplied by the American Jersey Cattle Association and test-day production data from 1970 through 1998 obtained from the Animal Breeding Center at Cornell University. Rate of increase in level of inbreeding is accelerating with time, making it more difficult for producers to make matings that avoid the potentially deleterious effects of inbreeding. Production losses caused by inbreeding were significant and curvilinear for all traits studied except somatic cell linear score, with the greatest losses at higher levels of inbreeding. Inbreeding was found to have the greatest effect on production at early ages and early in lactation. Early onset of the deleterious effects of inbreeding resulted in larger net present value losses than if effects of inbreeding occurred later in the life of an animal. Losses were probably enhanced because of the need to freshen animals as early as possible to maximize net present value returns. Survival decreased as level of inbreeding increased and was likely to have a greater negative impact on the financial health of the dairy enterprise than production losses.

Age Factors↗
PubMed2000

Transcriptional regulation of the cellular retinoic acid binding protein I gene in F9 teratocarcinoma cells.

Retinoic acid (RA) induces the differentiation of many murine teratocarcinoma cell lines such as F9 and P19. In F9 cells, the level of the cellular retinoic acid binding protein I (CRABP I) mRNA is greatly reduced after exposure of the cultured cells to exogenous RA. In P19 cells, the level of CRABP I mRNA is greatly increased after RA exposure. We have identified a 176-bp region in the murine CRABP I promoter, between -2.9 and -2.7 kb 5' of the start site of transcription, which acts as an enhancer in undifferentiated F9 stem cells and through which RA effects inhibition of CRABP I transcription. Within this region are two footprinted sites at -2763 and -2834. This 176-bp regulatory region does not function to enhance CRABP I transcription in P19 stem cells. Several DNA sequences within these two footprinted regions bind proteins from F9 nuclear extracts but not from P19 nuclear extracts (e.g., FP1B, FP1A, and FP2B), as assessed by gel shift assays. This 176-bp CRABP I genomic region has not been sequenced previously and functionally analyzed in cultured cells because it was not present in the murine CRABP I clones used for the promoter analyses reported earlier by another laboratory. The function of this enhancer may be to reduce the expression of the CRABP I gene in specific embryonic cell types in order to regulate the amount of RA to which the cells are exposed.

Animals↗
PubMed2000

Lymphosarcoma of the pharyngeal region in a 7-month-old beef steer.

A steer presented for retropharyngeal swelling and dyspnea. Biopsy of the swelling indicated lymphoblastic lymphosarcoma, and necropsy revealed involvement of regional veins and arteries. The tumor was classified as a non-T, non-B lymphoma based on CD3 polyclonal antibody stains. Lymphosarcoma is unusual in this location, but should be considered with retropharyngeal swelling.

Animals↗
PubMed2000

Skeletal and heart muscle protein turnover during long-term exposure to high environmental temperatures in young rats.

A study was undertaken to determine the long-term effects of a hot environment on protein turnover in skeletal and cardiac muscles of young homeothermic animals. Three groups of 36 male 28 day old rats were housed at 35 degrees C (hot group), 25 degrees C (control group), or 25 degrees C but pair-fed to the intake of the hot group (pair-fed group). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. By day 20, soleus and gastrocnemius (skeletal muscle) protein masses were 7 and 14% lower in the hot group and 31 and 21% lower in the pair-fed group compared with the control group (P < 0.05). The fractional rate of protein synthesis (k(syn)) was on average 11% lower (P < 0.05) in the hot group compared with control rats and was not different from pair-fed rats. The fractional rate of skeletal muscle protein degradation (k(deg)) in hot rats was slightly lower than in control rats; k(deg) was on average 18% higher (P < 0.05) in the pair-fed group compared with the hot group and this difference appeared to be most prominent on day 5. In heart, by day 20, protein mass was 30% lower in the hot group and 40% lower in the pair-fed group compared with control rats (P < 0.05). k(syn) was on average 19% lower (P < 0.05) in the hot group compared with the control group, but not different from pair-fed rats. In the heart there were no differences in k(deg) among treatments. Plasma triiodothyronine (T3) concentration was lower in the hot group, but not in the pair-fed group, compared with controls. In conclusion, chronic exposure to hot environments was associated with lower skeletal and cardiac muscle mass and protein turnover; lower protein mass in this tissue was due to decreased k(syn); this is consistent with lower plasma T3 concentrations. In pair-fed rats, k(syn) was also reduced, but interestingly k(deg) was not, resulting in a greater loss of skeletal muscle mass. These results suggest that heat exposure invokes physiological adaptations to preserve skeletal muscle mass despite decreased food intake. In the heart, loss of protein was a result of decreased k(syn), which can be primarily ascribed to lower food intake.

Acclimatization↗
PubMed1999

Anatomy of pelvic arteries adjacent to the sacrospinous ligament: importance of the coccygeal branch of the inferior gluteal artery.

OBJECTIVE: To describe the arterial vascular anatomy in the area of the sacrospinous ligament. METHODS: Cadaver pelvises were dissected to reveal the anatomy of the sacrospinous ligament with emphasis on vascular and neuroanatomy. Flexible rulers were used to measure the coccygeal branch in five hemipelvises. RESULTS: The pudendal vessels and nerve pass immediately medial and inferior to the ischial spine (within 0.5 cm of the spine) and behind the sacrospinous ligament. The pudendal artery lies anterior to the sacrotuberous ligament, which passes behind the ischial spine to its attachment at the posterior ischial tuberosity. The inferior gluteal artery originates from the posterior or the anterior branch of the internal iliac artery to pass behind the sciatic nerve and the sacrospinous ligament. There is a 3- to 5-mm window in which the inferior gluteal vessel is left uncovered above the top of the sacrospinous ligament and below the lower edge of the main body of the sciatic nerve plexus. The coccygeal branch of the inferior gluteal artery passes immediately behind the midportion of the sacrospinous ligament and pierces the sacrotuberous ligament in multiple sites. The main body of the inferior gluteal artery leaves the pelvis by passing posterior to the upper edge of the sacrospinous ligament and following the inferior portion of the sciatic nerve out of the greater sciatic foramen. CONCLUSION: Sutures placed through the sacrospinous ligament at least 2.5 cm from the ischial spine along the superior border of the sacrospinous ligament and without transgressing the entire thickness are in an area generally free of arterial vessels.

Arteries↗
PubMed1999

The National Survey of Trabeculectomy. I. Sample and methods.

PURPOSE: The National Survey of Trabeculectomy was designed to evaluate current practices of glaucoma surgery in the United Kingdom and to determine the success and complication rates of trabeculectomy on a national basis. This paper reports the survey methods, levels of consultant activity, waiting times, indications for surgery and the demographic and clinical characteristics of the patient sample. METHODS: Consultant ophthalmologists performing trabeculectomy in the United Kingdom were studied. Four consecutive patients undergoing trabeculectomy under each consultant prior to 18 June 1996 were retrospectively sampled. Patients were followed prospectively and evaluated 6 and 12 months after surgery. Data were collected by self-administered postal questionnaires. To determine the effects of selection and reporting bias a validation study of 14 randomly selected units was also conducted. RESULTS: Three hundred and eighty-two consultants recruited 1454 eligible patients for analysis. The mean age of patients was 69.2 years (standard deviation 10.9) and 51.7% were male. The underlying diagnosis was primary open angle glaucoma in 89.2%, pseudoexfoliation glaucoma in 5.4%, normal tension glaucoma in 3.8% and pigmentary glaucoma in 1.6%. There was advanced visual field damage in 50.5% of the cohort by the time of listing. The main indications for surgery were failure of medication to control intraocular pressure in 57.1%, progressive visual field loss in 26.5% and progressive optic disc damage in 4.8%. Primary surgery was undertaken in 4.8% of patients. In 80% trabeculectomy was performed within 3 months of listing. However, almost a third of consultants considered individual patient's waiting time too long. Validation studies confirmed that systematic bias did not operate in the selection of patients for the survey or in the reporting of outcomes. CONCLUSION: The findings of this survey are representative of current practices of trabeculectomy by consultants throughout the United Kingdom and show considerable variation in practice. Failure to control intraocular pressure with topical medications was the main indication for surgery. Advanced glaucomatous visual field damage was present at the time of surgery in half the sample. Though most patients were operated on within 3 months of listing, almost a third of consultants considered the wait unacceptably long.

Age Factors↗
PubMed1999

The National Survey of Local Anaesthesia for Ocular Surgery. I. Survey methodology and current practice.

PURPOSE: To describe the current usage of the various techniques of local anaesthesia (LA) in the United Kingdom, and safety precautions taken. METHODS: An observational study of practice of LA in the whole of the United Kingdom was carried out over 3 months in late 1996. Staff in all ophthalmology theatres in the National Health Service were invited to report every LA given for the purpose of intraocular surgery during the first week, and thereafter to report adverse events only. RESULTS: Participation during the first week was calculated to be 72.8% overall. Anaesthesia techniques for intraocular surgery were: 70% LA alone, 5.8% LA with sedation and 24.2% general anaesthesia. LA techniques were: 65.6% peribulbar, 16.9% retrobulbar, 6.7% sub-Tenon's, 4.4% subconjunctival, 2.9% topical and 2.3% combinations. Of patients who were given LA, 96% were monitored, 84% had an anaesthetist available in theatres in case of a problem and intravenous access was established in 60%. CONCLUSION: Local anaesthesia is frequently used for intraocular surgery in the United Kingdom. A variety of techniques are used, and safety precautions are taken in most cases.

Anesthesia, Local↗
PubMed1999

The National Survey of Local Anaesthesia for Ocular Surgery. II. Safety profiles of local anaesthesia techniques.

PURPOSE: To describe the adverse events associated with local anaesthesia (LA) for intraocular surgery. METHODS: An observational study of practice of LA in the whole of the United Kingdom was conducted over 3 months in late 1996. Staff in all ophthalmology theatres in the National Health Service were invited to report every LA given for the purpose of intraocular surgery during the first week, and thereafter to report adverse events only. RESULTS: During the first week, the reported incidence of all adverse events within the orbit was 2.7%, and for 'systemic' adverse events it was 0.9%. Serious adverse events were reported in association with all LA techniques. In 3 months, 18 events were described as 'life-threatening' by respondents, and further patients were reported to have had epileptic fits or were transferred directly from the operating theatre to an intensive care unit. The voluntary nature of the survey introduces some bias from under-reporting, making the incidence of these severe events difficult to assess. Reported incidence of severe 'systemic' adverse events was similar for all LA techniques. CONCLUSIONS: Serious adverse events were reported in association with with all LA techniques. This implies that we should be prepared for such events in all patients who have intraocular surgery.

Adult↗
PubMed1999

The size and form of the medulla of human scalp hair is regulated by the hair cycle and cross-sectional size of the hair shaft.

Hairs were sampled from long-haired Caucasian females, and cross-sectional measurements were performed using a rotating profile method at fixed humidity (100%). The effect of the hair cycle on medullation was investigated by examining medulla size and form along the lengths of anagen and telogen terminal hairs and also from a composite model of the entire medulla, as produced from a full cycle's growth, by amalgamating the results from the anagen and telogen hairs. The effect of hair shaft cross-sectional size on medullation has been investigated by controlling any effect of the hair cycle on terminal hairs and by use of the maximal medulla size in short, fine (vellous) hairs from the same subjects. All terminal hairs were medullated for the majority of their lengths. The presence and size of the medulla, in terminal hairs, was profoundly affected by the hair cycle. It was largest early in anagen, where the medulla minor axis, major axis and cross-sectional area represented about 26%, 23% and 7% of the corresponding whole hair shaft parameters (at 100% humidity). The medulla was virtually absent towards the end of anagen. The shape of the medulla cross-section was less elliptical than that of the whole hair shaft and was close to circular. There was no significant change in medulla shape through anagen. The form of the medulla was also affected by the hair cycle; approximately, it was continuous for the first 50% of anagen, discontinuous for the next 25% and virtually absent or absent for the final 25%. The maximal size of the medulla, as occurred in early anagen, was markedly associated with the cross-sectional size of the whole hair shaft, both within terminal hairs and between all scalp hairs. The medulla was large in terminal hairs and small or absent in very small hairs. The proportion of the whole hair shaft occupied by the medulla increased with increase in hair size and reached a maximum in terminal hairs, in which the medulla minor axis represented about 30% of the whole hair shaft minor axis. Furthermore, this proportion was constant in the terminal hairs and was not related to whole hair shaft size. Such maximal proportional medullation might represent a defining feature of terminal hairs. Variation in size of the medulla is not the cause of the previously reported cycle-dependent change in cross-sectional size of the whole hair shaft of terminal hairs.

Female↗
PubMed1999

A glucan synthase FKS1 homolog in cryptococcus neoformans is single copy and encodes an essential function.

Cryptococcal meningitis is a fungal infection, caused by Cryptococcus neoformans, which is prevalent in immunocompromised patient populations. Treatment failures of this disease are emerging in the clinic, usually associated with long-term treatment with existing antifungal agents. The fungal cell wall is an attractive target for drug therapy because the syntheses of cell wall glucan and chitin are processes that are absent in mammalian cells. Echinocandins comprise a class of lipopeptide compounds known to inhibit 1,3-beta-glucan synthesis, and at least two compounds belonging to this class are currently in clinical trials as therapy for life-threatening fungal infections. Studies of Saccharomyces cerevisiae and Candida albicans mutants identify the membrane-spanning subunit of glucan synthase, encoded by the FKS genes, as the molecular target of echinocandins. In vitro, the echinocandins show potent antifungal activity against Candida and Aspergillus species but are much less potent against C. neoformans. In order to examine why C. neoformans cells are less susceptible to echinocandin treatment, we have cloned a homolog of S. cerevisiae FKS1 from C. neoformans. We have developed a generalized method to evaluate the essentiality of genes in Cryptococcus and applied it to the FKS1 gene. The method relies on homologous integrative transformation with a plasmid that can integrate in two orientations, only one of which will disrupt the target gene function. The results of this analysis suggest that the C. neoformans FKS1 gene is essential for viability. The C. neoformans FKS1 sequence is closely related to the FKS1 sequences from other fungal species and appears to be single copy in C. neoformans. Furthermore, amino acid residues known to be critical for echinocandin susceptibility in Saccharomyces are conserved in the C. neoformans FKS1 sequence.

Amino Acid Sequence↗