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Biomedical subjects

M Tucker

Publications and source records attributed to M Tucker.

At least 55 records · Page 3Linked to original sources
PubMed1995

Transdentinal stimulation of reparative dentine formation by osteogenic protein-1 in monkeys.

Recombinant human osteogenic protein-1 (OP-1) when applied to freshly cut dentine stimulated significantly more reparative dentine than calcium hydroxide paste in permanent monkey teeth. The response to OP-1 was dependent upon the concentration applied to the tooth as a cavity liner as well as the thickness of the residual dentine. The response to calcium hydroxide was similarly dependent upon the thickness of the residual dentine. These data suggest that dental pulps contain cells, including perhaps mature odontoblasts, responsive to OP-1. Therefore OP-1 may be useful in the therapeutic induction of reparative dentine formation.

Analysis of Variance↗
PubMed1994

V-sis induces Egr-1 expression by a pathway mediated by c-Ha-Ras.

The early growth response gene, Egr-1, is up-regulated transiently by mitogens and many other stimuli in all cells tested. Using NIH3T3 cells conditionally expressing v-sis from a metallothionein promoter, we show that the addition of Zn2+ stimulates the production of PDGF-B (v-sis) and elicits the expression of Egr-1 in a dose-dependent and time-regulated manner. The signal is likely independent of protein kinase C, but depends on tyrosine kinase and other kinase activities and is mediated by c-Ha-Ras since the presence of dominant-negative mutants of Ras and Raf abrogates the induction of Egr-1 expression by Zn2+. Transiently activated Ras expression in NIH3T3 cells also stimulates the transient expression of Egr-1, but cells that constitutively express Ras do not have elevated levels of Egr-1. Transient assays also demonstrated that Zn2+ or activated Ras expression stimulate the activity of a 950 bp Egr-1 promoter-reporter gene construct and this is abrogated in the presence of mutant Ras and Raf. The accumulated data show that Egr-1 gene expression is regulated by multiple mechanisms, as would be needed for putative roles in cell proliferation, in suppression of transformation and in differentiation.

3T3 Cells↗
PubMed1994

Measurement of chloride concentration in microvolume samples of sweat.

Measuring sweat Cl concentration requires multiple steps. Following pilocarpine iontophoresis we compared Cl concentrations of sweat obtained on gauze pads to microvolumes (5 microL) collected into capillary tubes (N = 111). Chloride concentrations obtained by these two methods correlated significantly (r = 0.95; P < 0.001), indicating that Cl concentration can be measured accurately and easily on small volumes.

Chlorine↗
PubMed1994

The time-course of the induction of reparative dentine formation in monkeys by recombinant human osteogenic protein-1.

Recombinant human osteogenic protein-1 (hOP-1, BMP-7) induces cartilage and bone formation when implanted in extra- and intraskeletal sites in vivo. rOP-1 also preserves pulp vitality and stimulates reparative dentine formation when placed on partially amputated vital dental pulp tissue. The amount of dentine formed in 6 weeks was earlier found to be proportional to the total amount of rOP-1/carrier placed on the pulp and the capacity of the pulp to respond to rOP-1 appeared to be independent of the amount of coronal pulp removed. This reparative dentine was not completely mineralized after 6 weeks healing. Experiments were now made to determine the capacity of hOP-1 to preserve the vitality of and induce reparative dentine in vital radicular pulps. The extent of tissue mineralization present after 1, 2, 4 and 6 months' healing time in permanent monkey teeth was assessed. Radicular pulp vitality was maintained, reparative dentine formed, and mineralization was nearly 75% complete after 1 month and more than 95% after 4 months. The effects of irrigating the exposed pulps with EDTA, sodium hypochlorite or saline were also compared. Significantly more sodium hypochlorite-treated pulps became non-vital and the root canals of all the non-vital teeth contained bacteria at the time of sacrifice.

Animals↗
PubMed1994

Effect of vanadate on reproductive efficiency in normal and streptozocin-treated diabetic rats.

The effects of oral vanadate treatment on the reproductive efficiency of normal and diabetic female rats were studied. Vanadate treatment in a dose-dependent manner reduced both the conception rate and the ability to carry pregnancy to term compared with a control group. These effects were more severe in diabetic groups as compared with nondiabetic groups. At the 0.25 mg/mL vanadate dose, the conception rate was reduced by 13% and 33% for the nondiabetic group and the diabetic group, respectively. At the 0.50 mg/mL dose, this rate decreased by 20% and 47% for the nondiabetic and diabetic groups, respectively. With an identical oral vanadate regimen of 0.25 mg/mL, the ability to sustain pregnancy to term was reduced by 30% and 90% for the nondiabetic and diabetic groups, respectively, and by 84% and 100% for these groups at a dose of 0.50 mg/mL. Although the blood vanadate concentrations were an order of magnitude higher in diabetic animals treated with vanadate than in nondiabetic animals under an identical vanadate treatment, oral vanadate treatments had no measurable effects in ameliorating hyperglycemia in these diabetic pregnant animals. In conclusion, vanadate is ineffective in normalizing blood glucose in pregnant diabetic rats, and it impairs reproductive capacity and the ability to sustain pregnancy to term in both nondiabetic and diabetic animals.

Administration, Oral↗
PubMed1994

Use of chromosome microdissection, the polymerase chain reaction, and dot blot hybridization to analyze double minute chromosomes.

The potential usefulness of chromosome microdissection, the polymerase chain reaction (PCR), and dot blot hybridization as a quick screening method for determining the genetic composition of double minute chromosomes (DMs) was evaluated. DMs or abnormally banding regions (ABRs) were microdissected from multidrug-resistant hamster cell lines and amplified with PCR using primers specific for the hamster multidrug-resistance (MDR) gene, pgp 1. The microdissected-PCR-amplified products were shown to (a) hybridize to a 32P-labeled pCHP1 probe for the hamster MDR gene by using dot blot or Southern blot analysis and also (b) hybridize back to the chromosome region from which they were originally dissected by using fluorescent in situ hybridization. Microdissected/PCR-amplified DMs were also shown to hybridize to ABRs. When microdissected DMs and ABRs were amplified using hamster specific Alu primers, the resulting material was shown to hybridize with probes for hamster MDR and Alu. These results suggest that the DMs contained in these MDR hamster cell lines contain Alu-like sequences and the chromosome microdissection-PCR-hybridization approach might be used as a quick screening method for identifying genes amplified in DMs and ABRs in cell lines and human tumor samples.

Animals↗
PubMed1994

Localization of connexin43 in rat kidney.

The localization of connexin43 (Cx 43) in rat kidney was investigated by the indirect immunofluorescence technique with polyclonal antisera raised against Cx 43. Cx 43 is a gap junction protein expressed in a variety of tissues. The typically punctuated gap junction immunofluorescence (GJI) was observed in the renal arterial and arteriolar system. In the renal artery the GJI was concentrated in the media. In the juxtamedullary nephrons, the GJI is particularly abundant in the vascular bundles. There is abundant GJI in the extraglomerular mesangium while in the afferent arteriole GJI appears decreased. Abundant GJI was observed in the inner medullary collecting ducts and pelvic epithelium. The localization of Cx 43 immunofluorescence observed in this study is only in partial agreement with the results of ultrastructural investigations on the distribution of gap junctions in the kidney. An extensive tight junctional system has been demonstrated in the collecting duct system. However, gap junctions have been reported to be absent. Further studies to resolve this discrepancy are required.

Animals↗
PubMed1994

Providing easy access to distributed medical data.

Many hospitals are fragmented along departmental boundaries, leading to islands of information about patients. This makes data integration difficult, and therefore can increase hospital costs and reduce patient care. This paper presents an architecture to provide uniform and transparent access to computerized data and functions available in this kind of heterogeneous computer environment.

Computer Communication Networks↗
PubMed1993

Occupational physical activity, socioeconomic status, and risks of 15 cancer sites in Turkey.

A multiple-site case-control study of 15 cancers (stomach; colon; rectum; larynx; lung; melanoma; skin; female breast; male breast; cervix; ovary; uterus; prostate; testis; and bladder) was conducted to evaluate their association with occupational physical activity and socioeconomic status (SES). A hospital-based study population (3,486 male cases and 379 female cases, and 2,127 male and 244 female controls) was established in an oncological treatment center in Istanbul, Turkey, from 1979-84. Assessment of physical activity and SES was based on job titles held by the study subjects. Two measures of physical activity were developed based on energy expenditure and 'sitting time' during working hours. Observed risks were adjusted for age, smoking, and SES. Elevated risks were observed among workers who held sedentary jobs for cancers of the colon (odds ratio [OR] = 1.6), rectum (OR = 1.3), melanoma (OR = 1.9), male breast (OR = 1.4), prostate (OR = 5.0), and ovary (OR = 2.0). Cancers of the cervix and uterus showed significantly decreasing risks with decreased activity. Risks of cancers of the colon, rectum, larynx, ovary, and melanoma were enhanced after risks for physical activity indices were adjusted for SES, while the associations between physical activity and cancers of the prostate, cervix, and uterus were weakened after SES adjustment. Risks of melanoma rose significantly with both activity indices after SES adjustment.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Induction of reparative dentine formation in monkeys by recombinant human osteogenic protein-1.

Osteogenic protein-1 (OP-1, BMP-7), a member of the transforming growth factor-beta supergene family, induces cartilage and bone formation when implanted in intra- and extraskeletal sites in vivo. The human OP-1 gene has been cloned and biologically active recombinant OP-1 homodimers (hOP-1) produced. The amount of bone induced by hOP-1 in vivo is related to the amount of protein implanted. Dentine possesses bone morphogenetic protein (BMP) activity. Impure material from allogenic bone with BMP activity induced reparative dentine formation in dogs. The objective of this study was to determine if the amount of reparative dentine stimulated by hOP-1 is related to the amount of protein utilized in direct pulp-capping experiments. Freshly exposed molar and premolar pulps were treated with varying amounts of a complex comprising hOP-1 and a carrier matrix of purified bovine type-1 collagen powder (CM) moistened with sterile saline. Reparative dentine was present in all hOP-1/CM treated teeth (12 of 15) that remained sealed for the 6 weeks' healing. Substantially more new dentine was present in teeth treated with hOP-1/CM than in those treated with Ca(OH)2 paste and the amount of reparative dentine formed was proportional to the amount of hOP-1/CM (P < 0.05). No reparative dentine formed in collagen carrier or untreated teeth. The appearances of the new tissue suggested that much of the mass of the hOP-1/CM was replaced first by a pulp-like connective tissue, which mineralized to form reparative dentine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Non-disjunction in human sperm: results of fluorescence in situ hybridization studies using two and three probes.

Fluorescence in situ hybridization using two or three probes was utilized to estimate the incidence of diploidy, the incidence of disomy for the sex chromosomes and chromosomes 16 and 18, and the proportion of Y- and X-chromosome bearing sperm, in a series of normal males. Our results demonstrate the importance of using an approach capable of distinguishing disomy from diploidy, as most donors had levels of diploidy higher than the disomy levels of individual chromosomes. Our analyses suggest the existence of chromosome-specific mechanisms of paternal non-disjunction, as sex chromosome disomy was approximately 1.5 times as common as disomy 16, and over two times as common as disomy 18. In studies of gametic sex ratio, we found little evidence for marked deviation from an expected 1:1 ratio.

Chromosomes, Human, Pair 16↗
PubMed1993

Human spermatozoal tail hypo-osmotic swelling test, motility characteristics in hypotonic saline, and survival of spermatozoa after cryopreservation.

Normozoospermic semen samples (n = 82) were examined to investigate whether the degree of sperm tail swelling in hypo-osmotic medium (fructose and sodium citrate; 150 mOsm/l), and motility characteristics after a 15-min exposure to hypotonic saline (sodium chloride; 150 mOsm/l) could predict the cryosurvival rate (% post-thaw motility/% pre-freeze motility x 100%) of spermatozoa after cryopreservation by the liquid nitrogen vapour freezing method using the TEST-glycerol-egg yolk buffer. The CellSoft automated semen analyser was used to analyse sperm motility in pre-freeze and post-thaw semen samples, and after exposure to hypotonic saline. Sperm tail hypo-osmotic swelling and sperm motility in pre-freeze semen showed no significant correlations (P > 0.05) with the cryosurvival rate. There were significant correlations (P < 0.05) between the cryosurvival rate and the following sperm motility parameters in hypotonic saline: % motility (r = 0.2846), motility index (% motility x curvilinear velocity; r = 0.2809) and % decrease in motility index from the baseline value in semen (r = 0.3378). The % decrease in motility index after hypotonic saline treatment was significantly less (P < 0.05) in the normal (> or = 50% cryosurvival rate; mean +/- SEM 5.9 +/- 3.2%; n = 33) compared with the subnormal (< 50% cryosurvival rate; 27.3 +/- 4.8%; n = 49) cryosurvival groups. This parameter was also determined, by multivariate discriminant analysis, to be capable of classifying each pre-freeze semen sample into either cryosurvival group with 69.5% accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Survival↗
PubMed1992

Validity and reliability of the Neurobehavioral Assessment Scale.

The Neurobehavioral Assessment Scale (NAS) was developed to measure the full range of behavioral functioning from fully alert to deep coma. This investigator-rated scale was evaluated in 60 patients undergoing conscious sedation for maxillofacial procedures. The results obtained on the NAS were reliable, as evidenced by high correlations between the rating of the two raters. The scale is also valid as determined by high correlations between the NAS and a standard scale, the Glasgow Coma Scale (criterion validity) and between the NAS and the Digit Symbol Substitution Test (behavioral validity). The NAS clearly distinguished between two levels of sedation (heavy and light). Furthermore, the NAS appears to be better able to discriminate among the different degrees of sedation in lightly sedated patients than the Glasgow Coma Scale.

Adolescent↗
PubMed1992

Selective assisted hatching of human embryos.

Overall results of assisted hatching by zona drilling using acidic Tyrode's solution performed during three randomised trials in 330 in vitro fertilisation (IVF) patients are presented. It was demonstrated retrospectively and prospectively that assisted hatching by zona drilling was effective in embryos with thick zonae (> 15 microns). This procedure is called selective assisted hatching. In order to investigate whether the success rate of embryos with thin zonae (< 13 microns) can be improved further, a fourth trial was executed in 40 consenting patients. Embryos with thin zonae were left intact in one group (control), while the outside of zonae of similar embryos were thinned with acidic Tyrode's solution. Results thus far indicate that embryos with thin zonae do not benefit from this technique. Embryonic implantation (fetal heartbeat per embryo) was high (26%-27%) in both arms of the trial, probably as a result of selective zona drilling of low prognosis embryos with thick zonae. A method is presented for quantifying zona hardening in human embryos. The exposure to acidic Tyrode's solution of each embryo was expressed as a function of the duration to pierce the zona and the diameter of the needle. Preliminary findings suggested that embryonic viability is correlated with zona hardening. In order to test the hypothesis that extracellular fragments may affect embryonic viability, small amounts of fragments were removed from embryos during assisted hatching. The pregnancy rate in 36 patients with extracted fragments was relatively high (41%) considering the poor morphology of the embryos involved.

Adult↗
PubMed1991

Poor implantation of cryopreserved reinsemination-fertilized human embryos.

OBJECTIVE: To investigate whether a poor rate of implantation after in vitro fertilization (IVF) was due to poor embryonic/endometrial synchrony during the original IVF cycle, we have cryopreserved reinseminated-fertilized embryos for later more synchronous replacement after thawing. The chance of implantation of fresh reinseminated fertilized human oocytes is approximately one tenth that of timely fertilized embryos. STUDY DESIGN AND DATA: Retrospective study of 35 original oocyte collections in which initial normal fertilization was 47.3% (129/273 oocytes), with 49.6% fertilization (67/135) upon reinsemination. Of these, 70 initially fertilized and 67 reinsemination-fertilized embryos were cryopreserved, and 50 initially fertilized and all 67 reinsemination-fertilized embryos were subsequently thawed with 72% and 63% cryosurvival, respectively, (not significant). SETTING: Private infertility clinic. RESULTS: In 11 cycles, 23 thawed initially fertilized embryos (group A) were replaced with a 21.7% implantation rate per embryo; in 10 cycles, 13 initially fertilized and 12 reinsemination-fertilized embryos (group B) were replaced together with an 8% implantation rate; finally, in 16 cycles, 30 reinsemination-fertilized embryos (group C) were replaced with a 3.3% implantation rate (group A versus group C: P = 0.076). Comparison of clinical pregnancies between these groups was significantly different (6/11 versus 1/16; P = 0.0427). CONCLUSION: Reinsemination-fertilized embryos survive freezing as well as initially fertilized embryos, but better embryonic/endometrial synchrony does not improve chances of their implantation.

Adult↗