Biomedical subjects

A T Davis

Publications and source records attributed to A T Davis.

At least 37 records · Page 2Linked to original sources

PubMed1997

Association of protein kinase CK2 with nuclear matrix: influence of method of preparation of nuclear matrix.

Nuclear matrix (NM) plays a role of fundamental structural and functional significance as the site of replication, transcription, and RNA processing and transport, acting as an anchor or attachment site for a variety of enzymes and other proteins involved in these activities. We have previously documented that protein kinase CK2 translocates from the cytosol to the nucleus, where it associates preferentially with chromatin and NM, in response to certain growth stimuli. Considering that characteristics of the isolated NM can depend on the procedural employed for its isolation, we compared three standard methods for NM preparation to confirm the association of intrinsic CK2 with this structure. Our data suggest that the method used for isolating the NM can qualitatively influence the measurable NM-associated CK2. However, all three methods employed yielded qualitatively similar results with respect to the stimulus-mediated modulation of NM-associated CK2, thus further supporting the notion that NM is an important site for physiologically relevant functions of CK2. In addition, core filaments and cytoskeleton that were isolated by two of the preparative methods had a small but significant level of associated CK2 activity.

Animals↗

PubMed1997

Nuclear matrix proteins as malignant markers in squamous cell carcinoma of the head and neck.

OBJECTIVE: To test the hypothesis that transformation of normal upper aerodigestive mucosa to squamous cell carcinoma of the head and neck (SCCHN) is associated with specific changes in nuclear matrix (NM) proteins. DESIGN: Retrospective, nonrandomized investigation using a cellular fractionation sequence followed by 2-dimensional gel electrophoresis analysis of NM proteins. SUBJECTS: Nuclear matrix proteins were extracted from a cohort of 12 pathologic SCCHN specimens and 5 normal specimens of oropharyngeal mucosa. RESULTS: All SCCHN specimens examined expressed 11 NM proteins that were not detected in normal mucosa. Conversely, at least 4 NM proteins that were expressed by all specimens of normal mucosa were absent from all SCCHN tumors. Seven NM proteins were common to carcinomas and normal specimens. Spindle cell histological variants of squamous cell carcinoma had distinct NM patterns. CONCLUSIONS: Malignant transformation of normal upper aerodigestive mucosa to SCCHN is associated with specific changes in NM composition. These data suggest that different NM proteins might serve as specific tumor markers.

Antigens, Nuclear↗

PubMed1997

In vitro studies of spontaneous and corticosteroid-induced apoptosis of lymphocyte populations from metamorphosing frogs/RU486 inhibition.

Metamorphosis in the South African clawed frog, Xenopus laevis, results in significant changes in the immune system. It is characterized by a striking involution of the thymus and spleen followed by lymphocyte expansion in the postmetamorphic period. While thyroid hormones are generally thought to be the most important mediators of morphological changes during metamorphosis, corticosteroid hormones (CH) have also been shown to accelerate metamorphic changes. We have been studying the possible role of CH as effectors of changes in the immune system at metamorphosis. Because CH induce apoptosis of developing murine thymocytes, we examined in vitro levels of spontaneous and CH-inducible apoptosis of lymphocyte populations removed from the thymus and spleen of tadpoles before metamorphosis, during the period of naturally elevated corticosteroids at the climax of metamorphosis, and from postmetamorphic adults. We show here that spontaneous apoptosis of splenocytes or thymocytes measurable at the time of sacrifice or after culture for 24 h at 4 degrees C is very low at all stages of development and is not increased at metamorphosis. Apoptosis induced by culture of lymphocytes for 24 h at 26 degrees C in 10 nM corticosterone (well below the peak level of 70 nM found at climax of metamorphosis) ranges from about 30-50% in the splenocyte population and 55-70% in the thymocyte population. Using the corticosteroid hormone receptor antagonist, RU486, we separated the CH-dependent component of apoptosis from apoptosis due to other factors. In the spleen, about 12-23% of lymphocytes are susceptible to corticosteroid-induced apoptosis at all larval stages as well as during climax of metamorphosis as measured by this short term culture assay. Another approximately 15% of cells undergo spontaneous apoptosis which is independent of CH. Although dissociated thymocytes exhibit very high levels of apoptosis (55-75%) during culture at 26 degrees C for 24 h, most of the apoptosis is independent of CH and may result from loss of "survival signals" due to the disruption of the thymic microenvironment. These studies support the hypothesis that naturally elevated levels of endogenous free CH delete a significant proportion of the larval splenocyte population during climax of metamorphosis by induction of apoptosis. This clearing of lymphocytes may prevent destructive autoimmune responses to the new set of adult-specific antigens that emerges at metamorphosis.

Animals↗

PubMed1997

Involvement of thyroid hormones in the expression of MHC class I antigens during ontogeny in Xenopus.

The major histocompatibility complex (MHC) is a cluster of genes encoding products central to all major functions of the vertebrate immune system. Evidence for an MHC can be found in all vertebrate groups that have been examined except the jawless fishes. Expression of MHC class I and class II antigens early in ontogeny is critically important for development of T lymphocytes capable of discriminating self from nonself. Because of this essential role in T-cell development, the ontogeny of MHC expression in the South African clawed frog, Xenopus laevis, was studied. Previous studies of MHC class I expression in Xenopus laevis suggested that class I antigens are virtually absent from tadpole tissues until climax of metamorphosis. We therefore examined the possible role of thyroid hormones (TH) in the induction of class I. By flow cytometry, a small amount of class I expression was detectable on splenocytes and erythrocytes in untreated frogs at prometamorphic stages 55-58, and the amount increased significantly at the conclusion of metamorphic climax. Thus, metamorphosis is associated with increased intensity of class I expression. Neither inhibition nor acceleration of metamorphosis altered the timing of onset of class I expression. However, inhibition of metamorphosis prevented the increase in class I expression characteristic of adult cell populations. Because expression was not accelerated in TH-treated frogs or delayed in metamorphosis-inhibited frogs, it is unlikely that TH are the direct developmental cues that induce expression, although they seem to be required for the upregulation of class I expression occurring at metamorphosis. Differences in the pattern of expression in different sub-populations of cells suggest a complex pattern of regulation of expression of class I antigens during ontogeny.

Animals↗

PubMed1997

Involvement of glucocorticoids in the reorganization of the amphibian immune system at metamorphosis.

In recent years, integrative animal biologists and behavioral scientists have begun to understand the complex interactions between the immune system and the neuroendocrine system. Amphibian metamorphosis offers a unique opportunity to study dramatic hormone-driven changes in the immune system in a compressed time frame. In the South African clawed frog, Xenopus laevis, the larval pattern of immunity is distinct from that of the adult, and metamorphosis marks the transition from one pattern to the other. Climax of metamorphosis is characterized by significant elevations in thyroid hormones, glucocorticoid hormones, and the pituitary hormones, prolactin and growth hormone. Previously, we and others have shown that elevated levels of unbound glucocorticoid hormones found at climax of metamorphosis are associated with a natural decline in lymphocyte numbers, lymphocyte viability, and mitogen-induced proliferation. Here we present evidence that the mechanism for loss of lymphocytes at metamorphosis is glucocorticoid-induced apoptosis. Inhibition of lymphocyte function and loss of lymphocytes in the thymus and spleen are reversible by in vitro or in vivo treatment with the glucocorticoid receptor antagonist, RU486, whereas the mineralocorticoid receptor antagonist, RU26752, is poorly effective. These observations support the hypothesis that loss of larval lymphocytes and changes in lymphocyte function are due to elevated concentrations of glucocorticoids that remove unnecessary lymphocytes to allow for development of immunological tolerance to the new adult-specific antigens that appear as a result of metamorphosis.

Aldosterone↗

PubMed1996

Assay for taurine conjugates of bile acids in serum by reversed-phase high-performance liquid chromatography.

The purpose of this study was to develop a new high-performance liquid chromatographic (HPLC) procedure for quantifying taurine conjugates of bile acids in serum. The technique involved three basic steps. The first removed free amino acids via solid-phase extraction of the serum. The second step involved the reaction of the extracted serum with the enzyme choloylglycine hydrolase, which liberated the taurine from the conjugated bile acids. The third step was the reversed-phase HPLC separation of o-phthalicdicarboxaldehyde derivatives of taurine. The assay provides a simple technique for determination of the total amount of taurine-conjugated bile acids in serum.

Bile Acids and Salts↗

PubMed1996

Evidence that casein kinase 2 phosphorylates hepatic microsomal calcium-binding proteins 1 and 2 but not 3.

We have extensively purified three of the hepatic microsomal intralumenal Ca2+-binding proteins, CBP1, CBP2, and CBP3, which were originally described by Van et al. [(1989) J. Biol. Chem. 264, 17494-17501]. These apparently homogeneous preparations showed only single 45Ca2+ binding bands. On the basis of the peptide sequence, CBP2 was found to be highly homologous with the previously described protein ERp72. Similarly, CBP3 was identical to calreticulin and CBP1 had some homology to calmodulin. Contrary to the report of Van et al. (1989), we found that CBP2 had little thiol:protein disulfide oxidoreductase activity. Of the three purified preparations, only CBP2 exhibited apparent intrinsic protein kinase activity. This activity was found to be due to contamination of the CBP2 preparation by an extremely low concentration of tightly bound casein kinase 2 (CK2). In line with this observation, the phosphorylation was inhibited by heparin, removed by antibody to CK2, and stimulated by spermine. Furthermore, CBP2 was readily phosphorylated in vitro by added CK2 but only slowly phosphorylated by several other protein kinases. Thus, the persistence of CK2 in a highly purified preparation of CBP2 along with several other lines of evidence presented in this study might suggest that the protein CBP2 is a physiologically relevant substrate for CK2. Furthermore, these data suggest that CK2 might be localized in the lumen of the endoplasmic reticulum and that the phosphorylation of CBP2 in the lumen may play a role in the chaperone activity attributed to this protein.

Amino Acid Sequence↗

PubMed1996

Interference in protein assays of biological specimens by vanadyl compounds.

Vanadyl ribonucleoside and orthovanadate are commonly employed as inhibitors of ribonuclease and protein phosphatase activities, respectively, in a variety of tissue preparations. We have observed that the presence of these agents in the tissue samples interferes in the measurement of their protein content using the Coomassie dye binding procedure. We have demonstrated that this interference in the protein assay can be overcome by including H2O2 at a final concentration of 0.1% in the protein assay medium prior to the addition of the dye reagent. This results in accurate measurements of the protein content in the tissue preparation containing vanadyl ribonucleoside or orthovanadate.

Animals↗

PubMed1996

Association of a mosaic chromosomal 22q11 deletion with hypoplastic left heart syndrome.

The atypical presentation of CATCH 22 raises several important concerns. First, in this patient, as in others, the heart defects were found in association with subtle facial abnormalities but with few of the other criteria normally seen in CATCH 22. This association alone may be sufficient to raise suspicion that an interstitial 22q11 deletion may be present. Second, the incidence of chromosome 22 deletions in parents of children with a 22q11 deletion (25%) suggests that siblings or subsequent fetuses may also be at risk. Parents with subtle or unusual manifestations of CATCH 22 may be unaware of their potential carrier status. Finally, the recognition of chromosomal mosaicism in this patient may have been fortuitous, as cytogenetic studies of leukocytes from other individuals with a mosaic karyotype may sometimes fail to reveal a 22q11 deletion that is present in cardiac tissues. Molecular cytogenetic analysis of cardiac specimens that are removed during routine surgical procedures may be warranted in appropriate clinical situations.

Chromosome Deletion↗

PubMed1996

beta-Hydroxybutyrate oxidation is reduced and hepatic balance of ketone bodies and free fatty acids is unaltered in carnitine-depleted, pivalate-treated rats.

These experiments were designed to determine whether carnitine depletion in the rat due to pivalate administration causes reduced beta-hydroxybutyrate oxidation and alterations in hepatic balance of ketone bodies and free fatty acids, relative to control rats. Male rats were given 20 mmol/L sodium pivalate for 2 wk to induce a secondary carnitine deficiency. Control animals were given 20 mmol/L sodium bicarbonate in their drinking water. In the ketone utilization experiment, rats were food-deprived for 24 h and infused with the sodium salt of beta-hydroxybutyrate to maintain total plasma ketone concentrations between 6.0 and 10.0 mmol/L. After a bolus of 3-hydroxy[3-14C]butyrate, the recovery of expired 14CO2 collected during the ensuing 100 min was significantly lower in the pivalate-treated rats than in the controls (P < 0.05). In the second experiment, blood samples from pivalate-treated and control rats were collected from the abdominal aorta, portal vein and hepatic vein to determine the hepatic balance (hepatic input - hepatic output) of ketone bodies and free fatty acids. No significant differences were seen between the two treatment groups for either ketone bodies or free fatty acids. We conclude that the higher plasma ketone concentrations seen in food-deprived, pivalate-treated rats were due to a lower rate of ketone utilization. No evidence of pivalate influence upon ketone production was found.

3-Hydroxybutyric Acid↗

PubMed1996

Carnitine supplementation ameliorates the steatosis and ketosis induced by pivalate in rats.

These studies examined the effect in rats of carnitine supplementation on variables of fat metabolism altered by administration of sodium pivalate, a compound which induces a carnitine deficiency. Weanling male rats received 20 mmol/L sodium pivalate or 20 mmol/L sodium bicarbonate in their drinking water for 2 wk. They were food-deprived for 24 h, and to maximize fatty acid oxidation, were cold-stressed for 4 h. In Experiment 1, group 1 received the bicarbonate, group 2 received the pivalate, group 3 received the pivalate and 0.46 mmol L-carnitine in the diet/d, while group 4 received the pivalate and 0.95 mmol L-carnitine in the diet/d. In Experiment 2, group 1 received unsupplemented drinking water, group 2 received the bicarbonate, group 3 received the pivalate, and group 4 received the pivalate and 0.95 mmol L-carnitine in the diet/d. Pivalate-treated rats given the low carnitine diet had plasma and liver triglyceride levels (Experiment 1), plasma beta-hydroxybutyrate concentrations (Experiments 1 and 2) and urinary dicarboxylic acid excretion (Experiment 2) significantly greater than those of controls (P < 0.05). The reduced tissue carnitine concentrations, starvation ketosis and lipid accumulation in the liver are findings also reported for human secondary carnitine deficiency due to organic acidurias. Supplementing the diet with L-carnitine at the level of 0.95 mmol/d significantly raised plasma and tissue carnitine concentrations and reduced the plasma beta-hydroxybutyrate and liver triglyceride concentrations to levels not significantly different than control values. Carnitine supplementation ameliorates the degree of liver lipid accumulation and exaggerated starvation ketosis induced by pivalate.

3-Hydroxybutyric Acid↗

PubMed1996

Children with chronic conditions in a pediatric emergency department.

The objective of this study was to describe the use of a pediatric emergency department (PED) by children with chronic conditions. The study design was retrospective and descriptive in an urban tertiary care pediatric hospital setting. We reviewed 8561 visits to a PED over a three-month time period. Two thousand twenty-four (24%) of the visits were by children with one or more chronic conditions. There were no interventions. The mean age of the patients was 4.9 years, and 61% were male. Thirty-one percent of the patients sought care between 8 AM and 5 PM Monday through Friday. Five subspecialty areas accounted for 86% of the chronic conditions seen: asthma (43%), neurology (15%), hematology/oncology (14%), neurosurgery (10%), and cardiology (4%). Twenty-eight percent of the chronically ill patients were admitted as compared to 11% of the nonchronically ill patients (P < 0.001). One percent of the chronically ill patients were admitted to the intensive care unit as compared to 0.03% of the nonchronically ill patients (P < 0.0001). It was concluded that children with chronic conditions account for one-quarter of all PED visits. Sixty-nine percent of those visits were made during evening/ nighttime hours or on the weekend. A relatively large percentage of these children were admitted. The pediatric emergency physicians provide an important service to both the children with chronic conditions and the subspecialists who care for them. PEDs may need to refine emergency department systems to serve this group of patients as efficiently and effectively as possible.

Adolescent↗

PubMed1996

The use of isoflurane anaesthesia in studies of carnitine metabolism in the laboratory rat.

The purpose of this study was to investigate the effect of isoflurane anaesthesia in the rat prior to decapitation on metabolites of interest in studies of carnitine metabolism. Male and female fed and starved rats were allocated to either the decapitation group, or to the anaesthesia-decapitation group. Six animals were allocated to each treatment. Within each gender and within feeding status, there were no significant effects of isoflurane anaesthesia with regard to plasma and liver carnitine, plasma beta-hydroxybutyrate and free fatty acids, or liver free fatty acids, triglycerides, free CoA, and acetyl CoA (P > 0.05). It was concluded that isoflurane anaesthesia can be used in studies of carnitine metabolism where the rat is used as a model.

3-Hydroxybutyric Acid↗

PubMed1996

Historical roots of cultural diversity in nursing: the New England Hospital for Women and Children.

This is an historical research about cultural diversity as it first emerged in early American nursing education and practice. The purpose of this research is to explore and analyze the unique philosophy of inclusion at the New England Hospital for Women and Children during the pre- and post-Civil War era. The methodology included the use of primary sources and a site visit to the New England Hospital for Women and Children, renamed the Dimock Health Center. The findings reveal that this institution was an early culturally diverse model for American society, nursing education, and practice. Seen through a prism, this institution provides a continuous source of historical pride in cultural diversity with implications for nursing education, practice, and research.

Cultural Diversity↗

PubMed1995

Superior nitrogen balance after laparoscopic-assisted colectomy.

BACKGROUND: Although early resumption of enteral feeding after gastrointestinal surgery results in improved nitrogen balance and lower infectious complications, no postoperative nutritional data after laparoscopic-assisted colectomy exists. OBJECTIVE: The authors prospectively compared nitrogen balance after laparoscopic-assisted colectomy versus open colectomy. METHODS: This is a series of colon resections (open, N = 10; laparoscopic-assisted, N = 9) at the Ferguson-Blodgett Hospital, Grand Rapids, Michigan, between January and March 1993. Nitrogen intake and 24-hour urine collections were performed on postoperative days 1, 3, and 7 for the analysis of total urinary nitrogen and urinary 3 methylhistidine-(3mH). RESULTS: The time to passage of flatus (4.7 +/- 0.6; 2.0 +/- 0.2), resumption of oral intake (6.1 +/- 0.7; 1.4 +/- 0.2; p < 0.05, Student's test), first bowel movement (5.2 +/- 1.0; 3.0 +/- 0.3; p < 0.05, Student;s t test), and discharge (10.3 +/- 1.3; 4.1 +/- 1.8; p < 0.05, Student's t test) occurred significantly earlier in the laparoscopic-assisted colectomy group. Overall hospital charges were lower in the laparoscopic-assisted colectomy group ($11,572 +/- $823 vs. $13,961 +/- $1050). The operative time was higher in the laparoscopic-assisted colectomy group (176 +/- 12 hours vs. 105 +/- 17 hours, p < 0.05,Student's test). Blood loss was higher in the open group (805 +/- 264 mL vs 217 +/- 32 mL, p < 0.05, Student's test). Urinary nitrogen losses were similar between the two groups; however, significantly more patients in the laparoscopic-assisted colectomy group achieved net positive nitrogen on day 3 (6/9; 0/10; p < 0.05, Fisher's exact test), and day 7 (9/9; 4/10; p < 0.05, Fisher's exact test). Infectious complications occurred less frequently in the laparoscopic-assisted colectomy group (0/9 vs. 4/10; p < 0.05, Fisher's exact test). CONCLUSIONS: Patients undergoing laparoscopic-assisted colectomy can achieve early resumption of enteral nutrition with earlier return to positive nitrogen balance compared with open colectomy. This may offer benefits of fewer infectious complications and lower cost of care.

Colectomy↗

PubMed1995

Adults in the pediatric emergency department: a fish out of water?

UNLABELLED: Adults (> 17 years) occasionally seek care in pediatric emergency departments (PED). We reviewed the records of adults treated in our PED from September 1992 to August 1993 to better understand their needs. Patients were classified based on their relationship to our hospital: 1) no previous medical care association (new), and 2) adult patients followed in our clinics for chronic diseases (chronic). Data were analyzed using frequencies and comparison of means by Student's t test or chi 2. A follow-up phone call or written survey was used to assess quality of care and satisfaction. Of 40,895 patients, 384 were adults (0.9%). Ages ranged from 18 to 73 years (median = 21 years, mean = 25 years) with 49% men. Most adults were seen between 3:00 PM and 10:59 PM; 84% were triaged as urgent or emergent. There were 140 new, and 230 chronic, patients. Fourteen were not classified because of lack of information. The mean age of new adults was 33 years, median 29 years; 53% were hospital employees. Forty percent of new adults had preexisting illnesses. Most common problems were cardiac/hypertension (27%), blunt trauma (22%), eye splash (13%), and lacerations (9%). Forty eight percent were transferred to an adult hospital, and 20% of transferred patients were admitted overnight. Chronic adult patients were younger (mean 21 years, P < 0.001); fever/infection (37%), minor trauma (17%), and gastro-intestinal problems (12%) predominated; 36% were admitted. The average time in the PED was 70 minutes for new and 202 minutes for chronic patients (P < 0.001). CONCLUSIONS: Chronic patients present with problems much like those of their younger counterparts, and the PED is prepared to manage them. New adult patients present with adult problems: chest pain, hypertension, blunt trauma, and eye foreign body, and the PED should be prepared to manage these.

Adolescent↗

PubMed1995

Carnitine depletion in rat pups of lactating mothers given sodium pivalate.

The purpose of this study was to determine the effect of pivalate administration in the pregnant and lactating rat upon tissue carnitine concentrations in 1- and 5-day-old rat pups, as well as in the lactating rats. At 17 days of gestation, 5 rats began receiving 20 mmol/l sodium pivalate in their drinking water, while an additional 5 rats (control) received equimolar NaHCO3. There were no significant differences in litter size, or in pup weights at day 1 (p > 0.05). However, the pups from the pivalate group did weigh significantly less at 5 days of age relative to the control group. Neonatal rats in the pivalate group had significantly depressed levels of total carnitine in plasma, heart and liver, relative to the control group, at both 1 and 5 days of age. Similar depressions were noted for the lactating rats from the pivalate group. This study demonstrates the utility of pivalate administration in depressing carnitine concentrations in newborn rats.

Animals↗

PubMed1995

Androgenic regulation of protein kinase CK1 in the prostatic cell.

We examined the androgenic regulation of protein kinase CK1 in rat ventral prostate cytosolic and chromatin fractions. On androgen deprivation, CK1 in both the nuclear and cytoplasmic compartments decreases slowly at a similar rate. Stimulation of regrowth in the prostate does not evoke an early differential modulation in the CK1 because it increased in both the cytosol and chromatin only by 24 h after androgenic stimulus. These changes in CK1 relate to its proposed role in cell regulation at mitosis and differ from those in protein kinase CK2 that demonstrates rapid modulations in the nuclear compartment under similar conditions.

Amino Acid Sequence↗