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Biomedical subjects

G W Davis

Publications and source records attributed to G W Davis.

At least 37 records · Page 2Linked to original sources
PubMed1995

The use of aqueous cetylpyridinium chloride as a transport medium for suspected tuberculous tissues from badgers.

Deterioration of tuberculous tissue specimens from badgers during transit in the post was simulated in the laboratory, and it was found that unpreserved tissues showing miliary lesions and initially producing a confluent growth of Mycobacterium bovis became culture-negative over a period of 4 days at ambient summer temperatures (>20 degrees C). These findings implied that false negative results may be obtained from specimens containing only small numbers of bacilli following delays of 2 days between collection and culture. A bench trial of cetyl pyridinium chloride and bromide as preservatives showed viable bacillary numbers were maintained well. A field trial of a 1% aqueous solution of the chloride salt as a transport medium was carried out on 666 split tissue submissions and a significantly improved isolation rate was found from the preserved samples, with 40 (93%) of the total of 43 isolates of M. bovis compared with 27 isolates (63%) when no preservative was used. Isolation using the guinea pig test was attempted on 354 of these samples and yielded 38 (93%) of the 41 isolates, compared with culture of preserved samples which yielded 39 isolates (95%), an insignificant difference. The use of this transport medium maximised cultural isolations, such that no significant gain was achieved by the continued use of the animal test.

Journal Article↗
PubMed1994

Retrograde signaling and the development of transmitter release properties in the invertebrate nervous system.

The dynamics of presynaptic transmitter release are often matched to the functional properties of the postsynaptic cell. In organisms ranging from cats to crickets, evidence suggests that retrograde signaling is essential for matching these presynaptic release properties to individual postsynaptic partners. Retrograde interactions appear to control the development of presynaptic, short-term facilitation and depression.

Animals↗
PubMed1994

Long-term regulation of short-term transmitter release properties: retrograde signaling and synaptic development.

The dynamics of presynaptic transmitter release are often matched to the physiological properties and functions of the postsynaptic cell. In organisms ranging from cats to crickets, evidence suggests that retrograde signaling is essential for matching these presynaptic release properties to individual postsynaptic partners. Retrograde interactions appear to control the development of presynaptic, short-term facilitation and homosynaptic depression through local, retrograde signaling at the synapse.

Animals↗
PubMed1993

A role for postsynaptic neurons in determining presynaptic release properties in the cricket CNS: evidence for retrograde control of facilitation.

Intracellular recording sin the cricket cercal system show that the synaptic terminals of a single sensory neuron can facilitate at one target, the medial giant interneuron (MGI), and simultaneously depress at another target, interneuron 10-3. A quantal analysis of transmission at these synapses demonstrates that facilitation and depression are properties of the presynaptic cell. For facilitating synapses contacting MGI, the mean quantal content (m), determined from the probability of the failures, increases for the second EPSP, while the quantal size (q) remains constant. Similarly, an analysis of depression for those synapses contacting 10-3 supports a presynaptic mechanism for depression. Since facilitation and depression are presynaptic and their expression at the synapses of a single, identified sensory neuron are correlated with the target interneuron, we conclude that these properties are regulated locally, at the synapse, possibly by an interaction with the postsynaptic cell.

Acoustic Stimulation↗
PubMed1991

Automated percutaneous discectomy.

Automated percutaneous discectomy is a new, safe procedure for treating herniated lumbar discs still contained by the annulus or posterior longitudinal ligament. In 1985, one of the authors reported a percutaneous nucleus aspiration technique using a 2-mm aspiration probe. This small probe produced minimal tissue damage, allowing the procedure to be done on an outpatient. In this series, 518 patients were treated using this technique for an overall success rate of 85%. Compensation patients, elderly patients, and patients with previous surgery were treated successfully using percutaneous discectomy on an outpatient basis. No intraoperative or postoperative complications occurred.

Adult↗
PubMed1991

Estimates of beef carcass intermuscular fat.

Three experienced persons evaluated 158 carcasses 24 h postmortem for USDA yield grade (YG) and quality grade factors, nine subcutaneous (SC) fat indicators, and four intermuscular (IM) fat indicators. Forty sides (YG 1.1 to 3.8) were selected for determination of chemical composition, two measures of cutability, and total IM fat from the round, loin, rib, and chuck. The IM fat estimates at the 12th rib, rib-plate juncture, and 5th rib were correlated with percentage of chemical fat (r = -.72, -.70, and -.55, respectively). Simultaneous consideration of YG factors accounted for 61% of the variation in chemical fat. Substituting the IM fat estimate at the 12th rib for adjusted fat thickness (AFT) in the equation explained 60% of the variation in percentage of chemical fat. An equation containing two IM fat estimates, marbling score and longissimus muscle area explained 68% of the variation in chemical fat. Simultaneous consideration of the YG factors accounted for 59% of the variation in boneless, closely trimmed (6 mm SC fat and no IM fat) retail cuts from the round, loin, rib, and chuck. Substituting the IM fat estimate at the 12th rib for AFT in the equation accounted for 65% of the variation. These data from a fairly uniform set of steer carcasses show that percentage of chemical fat and cutability can be reliably predicted from IM fat estimates and other traits that can be visually estimated on hot-fat trimmed carcasses.

Adipose Tissue↗
PubMed1991

Relationships between pork loin palatability traits and physical characteristics of cooked chops.

Pork loins (n = 72) were selected so that marbling scores would range from "practically devoid" to "abundant" in the longissimus muscle. Loin chops were cooked and rated by a trained six-member sensory panel. Physical and chemical characteristics were stratified according to marbling level (divided into 10 subclasses), muscle structure, shear force, overall palatability, and juiciness (each divided into three subclasses). The highest ratings for overall palatability were assigned to chops with high reflectance (685 nm), low moisture (70.1%), high i.m. fat (9.1%; or, high marbling score), low protein (19.4%), and low cooking loss (25.9%). Chops with the highest percentage of cooking loss were high in moisture content (75.59%), low in i.m. fat (1.78%), and high in protein content (21.54%). Differences in muscle structure, shear force, overall palatability, and juiciness were associated with differences in percentages of protein, moisture (whole tissue basis [WTB]) and fat (WTB). Pork loins with marbling between "practically devoid-plus" and "small" had (P less than .05) more protein and less fat (WTB) than loins with marbling scores between "modest" and "abundant." Loins with overall palatability ratings between 4.0 and 6.0 had more moisture and protein (P less than .05) than did loins with palatability ratings of 6.1 to 8.0. Selecting pork loins with "small" or less marbling, extremely open structure, a juicy rating of "slightly juicy," and an overall palatability rating of "like slightly" would identify fresh loins that had lower fat and(or) higher protein content.

Animals↗
PubMed1990

Effects of infused glucose, sodium and potassium chlorides and polyphosphates on palatability of hot-boned pork.

Longissimus muscle sections were excised from eight pork carcasses 1 h postmortem and sectioned into six .5-kg roasts to determine the effects of glucose, salt and polyphosphates (aqueous solution to 110% of fresh weight) on palatability of hot-boned pork. Treatments were hot-boned control (HB) with no infusion or infusions of 2% KCl and 3% of a 1:1 mixture of sodium hexametaphosphate and sodium pyrophosphate (PP) plus either 8% NaCl; 2% glucose (G) plus 6% NaCl; 6% G plus 2% NaCl; or 8% G. Another muscle section was chilled at 0 degrees C for 24 h on each carcass as a cold-processed control (CP). The roasts were frozen until cooked and evaluated by a sensory panel. The infused groups were more tender, juicy and salty and higher in moisture and ash but lower in protein content than either the CP or HB controls (P less than .05). The fat content of the infused groups was lower than of the HB control but was not different from that of the CP control. Either 2% NaCl plus 6% G or equal amounts (4%) of NaCl and G produced the most tender and juicy product. The substitution of 4% glucose for NaCl not only reduced the NaCl content of the infusion solution, but also improved the palatability of the meat. This substitution allows production of a hot-boned, lower-sodium precooked pork that is tender and juicy.

Animals↗
PubMed1989

Automated percutaneous lumbar discectomy.

Lumbar spine disc disease has traditionally been treated surgically by laminectomy and manual removal of the offending disc material. Chymopapain was extensively used to decompress the disc pressure in a relatively noninvasive manner, but has been abandoned due to serious complications, including anaphylaxis and paraplegia. Onik introduced automated percutaneous discectomy in 1985. This procedure has proved safe and efficacious for treating lumbar disc disease without complications. It is performed on an out-patient basis under local anesthesia with minimal rehabilitation time. The success rate reported in a multiinstitutional study with one year follow-up is approximately 75%. The majority of failures occur in patients with free fragments or spinal stenosis - both of which can be diagnosed preoperatively with good imaging examinations. Hence, the success rate can be expected to improve if preoperative imaging is relied upon to help choose appropriate patients. Over 30,000 percutaneous discectomy procedures have been performed. The only complication reported, disc infection, developed in fewer than 0.2% of cases. Automated percutaneous discectomy has the potential to treat a vast number of patients with lumbar disc disease who otherwise would have laminectomies.

Fluoroscopy↗
PubMed1989

Retrorenal colon: implications for percutaneous diskectomy.

It has been recommended that computed tomography (CT) with the patient prone be performed in every patient undergoing percutaneous diskectomy; this would enable detection of a retrorenal location of the colon, which could interfere with the percutaneous procedure. In this evaluation of 346 prone CT studies, only one patient (0.29%) was found to have retrorenal or retropsoas bowel that would have been perforated at diskectomy. Because of this extremely low prevalence, the performance of prone CT in every patient undergoing percutaneous lumbar diskectomy is not believed to be necessary.

Adolescent↗
PubMed1989

Clinical experience with automated percutaneous lumbar discectomy.

Percutaneous automated aspiration discectomy is a new procedure for treating uncomplicated herniated lumbar discs. In a series of 200 patients, followed for up to six months, the overall success rate was 77.5%. Workers' compensation claimants, elderly patients, and patients with previous surgery can be treated successfully using percutaneous discectomy. Patients were treated on an outpatient basis. Patients returned to work significantly sooner after percutaneous discectomy than after microdiscectomy or laminectomy. No intraoperative or postoperative complications occurred.

Adult↗
PubMed1989

Automated percutaneous discectomy at the L5-S1 level. Use of a curved cannula.

Previously, a major limitation to percutaneous disc decompression to relieve symptoms of sciatica was the inability to approach the L5-S1 level. Obstruction by the iliac crest prevented the instrumentation from entering the L5-S1 disc space. In this paper, the authors describe a curved cannula which can be placed down to the L5-S1 disc space over a straight trocar that has been anchored at the annulus. The cannula bends the flexible aspiration probe back into the plane of the disc so that it is no longer obstructed by the sacral end plate. Using this system, the L5-S1 disc space was successfully removed in 90% of 30 cases.

Catheterization↗
PubMed1987

Cholesterol concentration of longissimus muscle, subcutaneous fat and serum of two beef cattle breed types.

The cholesterol concentration of uncooked and cooked longissimus muscle, uncooked subcutaneous fat and serum, as affected by days on feed, breed type and sex class in a factorial arrangement, and the relationship between serum cholesterol and tissue cholesterol were studied. Days on feed, breed type and sex class had no effect (P greater than .05) on tissue cholesterol concentrations. Overall least-squares means for uncooked and cooked longissimus muscle and subcutaneous fat were 63.32, 80.27 and 98.90 mg of cholesterol/100 g of tissue, respectively. Cholesterol concentration was 26.8% higher in cooked vs uncooked muscle and 56.2% higher in uncooked subcutaneous fat compared with uncooked muscle. Serum cholesterol concentration was lower (P less than .05) for fullblood Chianinas and steers (122.6 and 133.9 mg/dl) compared with crossbreds and heifers (162.3 and 151.0 mg/dl), respectively. Serum cholesterol concentration showed a cubic response (P less than .05) over days on feed; it was lowest at 0 d (79.6 mg/dl), increased up to 77 d (156.3 mg/dl), leveled off (154.7 mg/dl), then increased again (179.3 mg/dl). Serum cholesterol had low and insignificant correlation coefficients with all tissue cholesterol concentrations (r = .08 to .22; P greater than .05). Results indicate that muscle and fat tissue cholesterol concentrations do not vary in response to the differences in breed type, sex class or time on feed represented in the present study and thus may be an inherent characteristic dependent upon quantitative needs for cellular membrane functions. However, serum cholesterol concentration was affected by treatments evaluated in this study and may be related to factors affecting lipid metabolism.

Adipose Tissue↗
PubMed1983

Conditioning of relative frequency of sniffing by rabbits to odors.

The sniff was identified by a brief episode of increased respiratory rate, usually with a well-defined time of onset. It was detected against the background of respiratory activity in rabbits simply, reliably, and noninvasively by statistical evaluation of digitized pneumograph records. The basal rate of exploratory sniffing was controlled by familiarization. Upon conditioning to olfactory cues, the rate of sniffing for CS+ increased sharply above the basal rate during the first 10 trials and was maintained at high levels by continued reinforcement. During extinction with discrimination between olfactory cues, the rate for CS- fell sharply at first and then more slowly toward the basal rate. With pseudoconditioning, the rabbits responded to an unpaired odor after several sessions; the rates of response acquisition and extinction and the maintained level of responding were lower than with a paired odor in classical delayed conditioning, and the response was not discriminative in respect to another novel odor given during extinction. The sniff displayed a prominent sensory bias for olfactory cues. The relative frequencies of sniffing and respiratory slowing were measured as conditioned responses by screening procedures with a small computer.

Animals↗
PubMed1982

A review of some statistical methods for covariance analysis of categorical data.

Three general methods for covariance analysis of categorical data are reviewed and applied to an example from a clinical trial in rheumatoid arthritis. The three methods considered are randomization-model nonparametric procedures, maximum likelihood logistic regression, and weighted least squares analysis of correlated marginal functions. A fourth heuristic approach, the unweighted linear model analysis, is an approximate procedure but it is easy to implement. The assumptions and statistical issues for each method are discussed so as to emphasize philosophical differences between their rationales. Attention is given to computational differences, but it is shown that the methods lead to similar results for analogous problems. It is argued that the essential differences between the methods lie in their underlying assumptions and the generality of the conclusions which may be drawn.

Adult↗