Biomedical subjects

C D Knight

Publications and source records attributed to C D Knight.

At least 37 records · Page 2Linked to original sources

PubMed1992

Impact of somatotropins on nutrient requirements in domestic animals.

Somatotropins increase nitrogen retention, decrease carcass fat and increase lean/fat ratio in growing ruminants and swine. However, responses are much more variable in growing ruminants. Maintenance requirements in both ruminants and swine are increased slightly with somatotropin treatment in conjunction with increased lean mass. This is associated with increases in partial efficiency of protein accretion, resulting in increased efficiency of growth. Additional information is required to accurately assess effects of somatotropin on nutrient requirements for growing ruminants and swine. Future studies should target degradable and nondegradable protein requirements for growing ruminants and the impact of somatotropin on these requirements; definition of dose, pattern and formulation of somatotropin for both ruminants and swine and interaction of somatotropin with other factors affecting feed intake in swine and ruminants.

Animals↗

PubMed1992

Effect of a hot environment on performance, carcass characteristics, and blood hormones and metabolites of pigs treated with porcine somatotropin.

A study was conducted to compare the effects of a single 100-mg recombinant porcine somatotropin (rpST) implant on performance, carcass characteristics, and blood hormones and metabolites of 40 finishing pigs exposed to either a thermoneutral (TN; 18 to 21 degrees C) or hot environment (H; 27 to 35 degrees C) for 28 or 35 d. Pigs in H gained at a slower rate (P less than .01) than pigs in TN. Control and rpST-treated pigs gained at similar rates in respective environments. The rpST-treated pigs consumed 13% less feed (P less than .01) than the control pigs in both environments, and pigs in H consumed 19% less feed (P less than .01) than pigs in TN. Feed efficiency for rpST-treated pigs was 15% better (P less than .01) than that for control pigs; environment had no effect on feed efficiency. When slaughtered, pigs treated with rpST had less (P less than .01) leaf fat and less (P less than .01) 10th rib backfat than control pigs. Pigs in H had a lower (P less than .01) final BW and less leaf fat and backfat than pigs in TN. The rpST and H had various effects on blood hormones and metabolites. The results demonstrated that the benefits of this form of rpST treatment achieved under TN were also achieved in H with no interactions between the hormone and environment.

Animals↗

PubMed1991

Stable transformation of the moss Physcomitrella patens.

We report the stable transformation of Physcomitrella patens to either G418 or hygromycin B resistance following polyethylene glycol-mediated direct DNA uptake by protoplasts. The method described in this paper was used successfully in independent experiments carried out in our two laboratories. Transformation was assessed by the following criteria: selection of antibiotic-resistant plants, mitotic and meiotic stability of phenotypes after removal of selective pressure and stable transmission of the character to the offspring; Southern hybridisation analysis of genomic DNA to show integration of the plasmid DNA; segregation of the resistance gene following crosses with antibiotic-sensitive strains; and finally Southern hybridisation analysis of both resistant and sensitive progeny. In addition to stable transformants, a heterogeneous class of unstable transformants was obtained.

Blotting, Southern↗

PubMed1991

Genetic analysis of a mutant class of Physcomitrella patens in which the polarity of gravitropism is reversed.

In the moss Physcomitrella patens, single-cell protonemata and multicellular gametophores respond to reorientation relative to the gravity vector by growing negatively gravitropically. A mutant class in which the protonemata, but not the gametophores, respond by growing towards gravity has been identified. In this paper, we describe the isolation of additional mutants of this class. Complementation and segregation ratio analyses were carried out on these mutants, which indicate that a single gene may mutate to switch the polarity of gravitropism.

Cell Separation↗

PubMed1991

The performance and carcass composition responses of finishing swine to a range of porcine somatotropin doses in a 1-week delivery system.

Four experiments using 580 barrows and 580 gilts (Study 1) and seven experiments using 500 barrows and 500 gilts (Study 2) were conducted at various geographical locations in the United States to determine the dose response of a pelleted form of porcine somatotropin (pST) relative to ADG, feed/gain (F/G), and percentage of carcass protein. Average initial weights for Studies 1 and 2 were 67.6 and 72.6 kg, respectively, and four pigs/pen were slaughtered when they achieved weights of 106.5 to 111.0 kg. In Study 1, pigs were implanted subcutaneously with pelleted pST doses of 0, 12, 24, 36, or 48 mg/wk and self-fed a corn-soybean meal diet containing 13.75% CP. Study 2 included two control groups self-fed a diet containing either 13.75 or 17% CP with added lysine. The pST-treated pigs were administered 12, 24, or 36 mg/wk, and all were offered the 17% CP diet. The pST treatments in Study 1 resulted in a linear reduction (P less than .05) in average daily feed intake (ADFI) and a quadratic (P less than .05) improvement in F/G and percentage of carcass protein. The pST treatments in Study 2 resulted in a linear reduction in ADFI (P less than .05), a linear improvement in F/G, and a quadratic increase in the percentage of carcass protein (P less than .05). Average daily gain was not affected in either study with this form of pST. The greatest increase in efficiency of lean gain was observed with the 36-mg dose for both Study 1 (9.4%) and Study 2 (10.8%). In Study 1, the force required to shear cores of the longissimus muscle was increased linearly with pST treatment (P less than .05). There was a similar linear increase in Study 2 with pST treatment (P less than .05); however, there was also an effect of sex (P less than .05) on shear force (gilts greater than barrows) that was similar in magnitude to that observed for pST treatment. Differences in sensory evaluation because of pST were minor and of the same magnitude as those observed between barrows and gilts. It was therefore concluded that weekly administration of pST improved F/G and percentage of carcass protein with no detrimental effects on palatability of cooked lean pork.

Animals↗

PubMed1991

Developmental genetic studies of the moss, Physcomitrella patens.

The development of the haploid gametophyte stage of Physcomitrella patens presents excellent opportunities for the detailed study of plant morphogenesis at the cellular level. The filamentous protonema undergoes a number of developmental transitions that can be observed directly in living material using time-lapse video microscopy and that can be manipulated both by treatment with phytohormones and by environmental stimuli. Mutants affecting these processes can be isolated and can be analysed using conventional as well as parasexual methods. Molecular biological techniques are now being established since these will be essential if the mechanisms that bring about morphogenetic processes are to be understood at the molecular level. A technique for genetic transformation has been devised and is being exploited to attempt to tag developmentally-relevant genes using maize transposons. Changes in gene activity associated with developmental transitions and in response to treatment with phytohormones and environmental stimuli are being studied using cDNA library subtraction techniques. Heterologous genes involved in the control of transcription and of the cell cycle are being used to probe the P. patens genome to identify possible homologues involved in developmental regulation.

Cytokinins↗

PubMed1990

The double stapling technique for low anterior resection. Results, modifications, and observations.

Since the introduction of the end-to-end anastomosis (EEA) stapler for rectal reconstruction, we have used a modification of the conventional technique in which the lower rectal segment is closed with the linear stapler (TA-55) and the anastomosis is performed using the EEA instrument across the linear staple line (double stapling technique). Our experience with this procedure includes stapled colorectal anastomoses in 75 patients and is the basis for the report. This review presents the details and advantages of the technique and the results. Complications include two patients with anastomotic leak (2.7%), and two with stenosis that required treatment (2.7%). Protective colostomy was not done in this series. There were no deaths. Our experience and that of others suggests that this modification of the EEA technique can allow a lower anastomosis in some patients, and that it can be done with greater safety and facility.

Aged↗

PubMed1989

The genetic analysis of tropic responses.

An increasing number of studies on tropic responses includes the genetic analysis of mutants defective in these morphogenetic processes. This review collates the information and discusses the implications of this approach to such studies. The review is organized on a systematic basis because most genetic analyses are insufficiently complete for general principles to have emerged. The most advanced analyses are those of lower eukaryotes because of their haploidy and the ease with which they can be manipulated in vitro. The extensive studies of phototropism, gravitropism and autochemotropism in the fungus Phycomyces blakesleeanus and of phototropism, polarotropism and gravitropism in the moss Physcomitrella patens are reviewed. In comparison with these studies, the genetic analysis of tropic responses in particular species of flowering plants is more limited. However, comparative physiological and ultra-structural studies of individual mutant and wild-type strains have been performed for a number of species. These results are discussed with particular regard to their support for established hypotheses.

Bryopsida↗

PubMed1988

Absorption of 14C-2-hydroxy-4-(methylthio)butanoic acid (Alimet) from the hindgut of the broiler chick.

The purpose of these studies was to examine the role of the hindgut of the broiler chick in the absorption of 2-hydroxy-4-(methylthio)butanoic acid (HMB). When 14C-HMB was delivered directly into the hindgut, the rate of absorption from this gastrointestinal site was about 40% of the administered dose per hour. Plasma radiolabel appearance indicated that the 14C-HMB lost from the hindgut was being absorbed into the bloodstream of the bird. Decarboxylation experiments using cecal microorganisms showed that the loss of 14C-HMB could not be accounted for by bacterial metabolism. When birds were dosed with radiolabelled HMB and tissue samples were tested, results showed that the 14C-HMB that was absorbed from the hindgut was incorporated into protein in a dose-related manner. In addition, an equimolar, equal specific activity intraperitoneal dose of HMB did not alter the rate of HMB adsorption from the hindgut. This indicates that HMB absorption from the gut is not limited by HMB already in the body tissues. This result confirmed that the rate of HMB diffusion into the blood and its conversion to methionine in body tissues were sufficient to maintain the concentration gradient required for the continued absorption of HMB. Finally, whole body autoradiography comparing 35S-HMB and 35S-DL-methionine showed no substantial differences in terms of label density or distribution. These studies demonstrate that 14C-HMB disappears from the lumen of the large intestine and ceca when it is administered directly into the hindgut. This research confirms that HMB is absorbed throughout the entire gastrointestinal system.

Animals↗

PubMed1986

Nodulation inhibition by Rhizobium leguminosarum multicopy nodABC genes and analysis of early stages of plant infection.

During analysis of early events in the infection and nodulation of Vicia hirsuta roots inoculated with normal and mutant strains of Rhizobium leguminosarum and strains containing cloned nodulation (nod) genes, a number of novel observations were made. (i) Alternating zones of curled and straight root hairs were seen on roots of V. hirsuta inoculated with the wild-type strain of R. leguminosarum. This phasing of root hair curling was not seen if plants were grown under continuous light or continuous dark conditions. (ii) Reduced nodulation and delayed nodule initiation was observed with a strain carrying a Tn5 mutation in the nodE gene. In addition the phased root hair curling was absent, and root hair curling was observed along the length of the root. (iii) The nodABC genes cloned on a multicopy plasmid in a wild-type strain inhibited nodulation but induced a continuous root hair curling response. Those few nodules that eventually formed were found to contain bacteria which had lost the plasmid carrying the nodABC genes. (iv) With a strain of Rhizobium cured of its indigenous symbiotic plasmid, but containing the cloned nodABCDEF genes, continuous root hair curling on V. hirsuta was observed. However, no infection threads were observed, and surprisingly, it did appear that initial stages of nodule development occurred. Observations of thin sections of these early developing nodules indicated that early nodule meristematic divisions may have occurred but that no bacteria were found within the nodules and no infection threads were observed either within the nodule bumps or within any of the root hairs. It was concluded that for normal infections to occur, precise regulation of the nod genes is required and that overexpression of the root hair curling genes inhibits the normal infection process.

Bacterial Proteins↗

PubMed1986

Surgical considerations after chemotherapy and radiation therapy for inflammatory breast cancer.

Eighteen patients seen between 1974 and 1982 with the clinical diagnosis of inflammatory breast carcinoma underwent modified radical mastectomy after preoperative chemotherapy and radiation therapy. In 17 of the 18 patients (94%), residual carcinoma was detected in either the resected breast or the axillary nodes. All mastectomies were accomplished without major technical difficulty. Seven wound complications, including three infections, occurred. Local recurrence was noted in 29% (five of 17 patients) and distant metastasis was detected in 89% (16 of 18 patients). Only three patients are presently alive without evidence of disease 19, 21, and 21 months since the onset of symptoms. Eleven patients have died, the median survival being 23 months since the development of symptoms, and four are alive with distant metastasis. Modified radical mastectomy can be accomplished in patients with inflammatory breast cancer after preoperative chemotherapy and radiation therapy and may have a role in reducing local tumor burden.

Adult↗

PubMed1985

Fibrolamellar hepatoma.

We found the clinical features of fibrolamellar hepatoma similar to those of nonfibrolamellar hepatoma with the exception of patient age. Although the histopathologic findings of fibrolamellar hepatoma are distinct and easily recognizable, we found that fibrolamellar hepatomas may be histologically heterogeneous. The overall length of survival of patients with fibrolamellar hepatoma was greater than that of patients with nonfibrolamellar hepatoma, but the survival resection was similar, regardless of histologic characteristics. Differences in overall survival between histologic subtypes probably reflects differences in the rate of resectability between fibrolamellar and nonfibrolamellar hepatomas.

Adolescent↗

PubMed1985

Gastric adenocarcinoma complicating Gardner's syndrome in a North American woman.

Gastric carcinoma has not been recognized as a complication of Gardner's syndrome in the Western world. We report a 37-yr-old white woman with Gardner's syndrome who had gastric adenocarcinoma in association with diffuse gastric polyps. At the time of laparotomy, the disease was metastatic to regional lymph nodes. In addition, the patient had mesenteric and retroperitoneal fibromatosis, thyroid adenomas, a chest wall hemangioma, and fibrocystic disease of the breast. This is the first reported case of gastric adenocarcinoma complicating Gardner's syndrome in North America.

Adenocarcinoma↗

PubMed1985

Duodenal duplication cyst causing massive bleeding in an adult: an unusual complication of a duplication cyst of the digestive tract.

Duodenal duplication cysts are rare malformations that characteristically manifest with intestinal obstruction. In a 50-year experience, we found a duodenal duplication cyst in only three patients, one of whom had massive gastrointestinal bleeding as the initial symptom. Six other duplication cysts (two esophageal, one jejunal, and three ileal) were found. All patients who had extraduodenal intestinal cysts were neonates or infants who initially had an abdominal mass or obstruction. Of the two patients with an esophageal cyst, one had odynophagia and the other had respiratory obstruction. Unusual features of our series of patients were male preponderance (eight of nine patients), the low incidence of other developmental abnormalities, and, in the patients with the duodenal cysts, an age of 14 years or older at the time of onset of symptoms and diagnosis. In an adult, a duodenal duplication cyst may cause upper gastrointestinal hemorrhage. This cause of gastrointestinal bleeding should be considered in the differential diagnosis if an intramural duodenal mass is detected within the medial wall of the second portion of the duodenum distal to the papilla of Vater.

Adult↗

PubMed1985

The legume-Rhizobium symbiosis: a cell surface interaction.

This review will examine the early stages of infection of legume roots by strains of Rhizobium that induce nitrogen-fixing nodules. The object is to show that, at least in terms of ultrastructure, the interactions between the plant and the rhizobia occur at the cell surface interface between these organisms. This situation exists at all stages, from the time the bacteria attach to the surface of the root hairs to the time they occur as the nitrogen-fixing form in the cytoplasm of the nodule cells, enclosed by peribacteroid membranes.

Cell Adhesion↗

PubMed1985

Rhizobium leguminosarum genes involved in early stages of nodulation.

Nodulation genes from Rhizobium leguminosarum have been subcloned and transferred to a strain of R. phaseoli with its symbiotic plasmid deleted (and therefore its nodulation and nitrogen fixation genes). Normal infection and nodule development occurred when these strains were added to the roots of Pisum sativum (peas) and Vicia hirsuta. The pea nodules were examined by electron microscopy; bacteroid forms were seen surrounded by peribacteroid membranes and using immuno-gold labelling it was shown that the nodule cells contained leghaemoglobin within the cytoplasm. By subcloning and analysing the nodulation region it was found that a small (3.2 X 10(3) bases) fragment of DNA contained three genes involved in root hair curling, the first observed step in the interaction between R. leguminosarum and the root hair cells of these legumes.

Cell Membrane↗

PubMed1984

Stapling technique for primary and secondary rectal anastomoses.

The EEA stapler now offers an alternative to hand-sewn techniques for primary and staged low colorectal anastomoses. The stapler may allow a safer and lower resection than was previously possible. A review of 52 primary and 8 staged EEA anastomoses is presented, with emphasis on the combined stapler technique.

Evaluation Studies as Topic↗

PubMed1984

Comparative absorption of 2-hydroxy-4-(methylthio)-butanoic acid and L-methionine in the broiler chick.

The absorption of [1-14C]2-hydroxy-4-(methylthio)butanoic acid (HMB) and L-methionine (L-Met) was evaluated in the broiler chick. Methods included in vitro intestinal tissue uptake and appearance in the plasma from ligated intestinal segments in situ, and from crop intubations. Intestinal uptake of L-Met was partially inhibited with 2,4-dinitrophenol, while HMB uptake was unaffected. The uptake of L-Met conformed to Michaelis-Menten kinetics except that no plateau was reached. This indicated that L-Met absorption may be accomplished by both concentration and energy-dependent processes. The in vitro uptake of HMB in relation to concentration was linear indicating that its absorption was concentration dependent. Absorption of HMB and L-Met after crop intubation indicated higher plasma concentrations of HMB than of L-Met, particularly at higher doses. Both compounds were absorbed at similar rates at concentrations 50-100 times below physiological concentrations and absorption rates were different at different small intestinal locations. These results indicate that the ability to use HMB as a source of methionine would not be limited by absorption.

2,4-Dinitrophenol↗