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Biomedical subjects

D M Wallace

Publications and source records attributed to D M Wallace.

At least 73 records · Page 4Linked to original sources
PubMed1987

Doppler evaluation of umbilical venous and arterial blood flow in the second and third trimesters of normal pregnancy.

Duplex Doppler ultrasound was used to measure umbilical venous blood flow in 209 normal pregnant women between 20-40 weeks' gestation. The relationship between umbilical venous blood flow and gestational age increased with gestational age, and is described by the equation y = -187.02 + 12.7x. The relationship between flow per kilogram fetal weight and gestational age (y = 198.629 - 2.24x) yielded values of 153 mL/minute/kg at 20 weeks, 131 mL/minute/kg at 30 weeks, and 108 mL/minute/kg at 40 weeks. Doppler ultrasound was also used to evaluate umbilical arterial waveforms (systolic/diastolic ratio) in 171 normal pregnant women between 20-40 weeks. The relationship between systolic/diastolic ratios and gestational age (y = 6.46 - 0.12x) decreased with advancing gestational age, yielding mean systolic/diastolic ratios (+/- 2 SD) of 4.1 (5.6, 2.6) at 20 weeks, 3.6 (5.1, 2.1) at 24 weeks, 3.1 (4.6, 1.6) at 28 weeks, 2.6 (4.1, 1.1) at 32 weeks, 2.1 (3.6, 0.6) at 36 weeks, and 1.7 (3.1, 0.1) at 40 weeks.

Blood Flow Velocity↗
PubMed1987

Duplex Doppler ultrasound in the evaluation of growth in twin pregnancies.

Fifty-six multiple pregnancies were evaluated for evidence of discordant growth using traditional ultrasonic methods and duplex Doppler ultrasound. The pregnancies consisted of 52 sets of twins and four sets of triplets. Duplex Doppler ultrasound predicted normal growth in 44 of 45 normal sets of fetuses, and correctly predicted discordant growth in nine of 11 discordant sets of twins. Among those nine abnormal sets, Doppler ultrasound predicted that six would become discordant before this was recognized by traditional ultrasonic measurements. Duplex Doppler ultrasound is useful in predicting and confirming concordant and discordant growth, and defining the cause of fetal discordancy.

Adult↗
PubMed1985

A comparison of bipolar and monopolar diathermy probes in experimental animals.

The effects of monopolar and bipolar diathermy were studied in laboratory animals. The power required to coagulate transected vessels in air was established and the effect of immersion in saline and water during electrocoagulation was investigated. Tissue heat conduction from each type of probe was measured and compared. Tissue damage was assessed by light microscopy of histochemically stained sections. The bipolar system operated at a lower power output (13 W) with less heat conduction, and was unaffected by the surrounding medium.

Animals↗
PubMed1985

Hazardous lead release from glazed dinnerware: a cautionary note.

Numerous pieces of contemporary glazed pottery dinnerware made in Italy and Mexico have been shown to release excessive amounts of lead, greater than 1000 ppm in several instances. Extended use with frequent scouring increased the lead release. This pottery, manufactured under obsolete conditions, may be imported into the United States by tourists, retail merchants and immigrants, and used for daily cooking and storage of food and beverages. Our findings demonstrate a potentially widespread health hazard both in the countries of origin of the pottery and the countries of importation.

Adult↗
PubMed1985

The influence of retinoic acid receptor (RAR) status of bladder tumours on the course of the disease.

Retinoids influence bladder tumour development in animals and tumour recurrence in man. Some human tumours contain intracellular receptor proteins for retinoids. The effect of the presence of such retinoic acid receptors (RAR) on tumour response to conventional therapy has been studied in 59 patients. Thirty-two of 36 RAR+ve and 11 of 23 RAR-ve tumour patients were alive after a mean follow-up period of 2.6 years. Higher stage and grade were more commonly associated with RAR-ve tumours. Independent of stage, recurrence was more common in RAR-ve tumours. These studies suggest that RAR-ve tumours are more likely to recur and more likely to become invasive. However, further studies are required to determine the clinical value of RAR receptor status as a prognostic indicator.

Carrier Proteins↗
PubMed1984

Promotion of bladder tumours by endoscopic procedures in an animal model.

An experimental study was performed to assess the possible tumour-promoting action of urothelial trauma caused by repeated intravesical diathermy, catheterisation, and the instillation of water, glycine and saline in the rat bladder which had previously been exposed to an initiating dose of the carcinogen N-methyl-N-nitrosourea. An increase in tumours and inflammatory changes was observed, especially in the group treated with water, and the significance of the findings is discussed.

Animals↗
PubMed1983

Reverse transcriptase and its associated ribonuclease H: interplay of two enzyme activities controls the yield of single-stranded complementary deoxyribonucleic acid.

The synthesis of single-stranded globin cDNA by the RNA-directed DNA polymerase activity of reverse transcriptase in the presence of oligothymidylate primers was investigated in order to determine the limitations to higher yields. The results indicated that the associated ribonuclease H activity, an integral part of reverse transcriptase, plays a large role in the synthesis of the first strand of cDNA and that the interplay of the two enzyme activities for any specific set of conditions determines the yield of single-stranded products. In both the presence and the absence of polymerization, the associated ribonuclease H catalyzed the deadenylation of mRNA, producing molecules that were somewhat shorter, highly homogeneous in size, and fully translatable into globin protein. They were also entirely lacking in the ability to serve as templates for cDNA synthesis. The reaction was completely dependent on oligothymidylate and completely independent of deoxyribonucleoside triphosphates. The initial rate of deadenylation was one-fourth the initial rate of initiation of polymerization when saturating levels of deoxyribonucleoside triphosphates were used in the polymerase reaction. In the presence of ribonuclease H activity, the DNA polymerase catalyzed the synthesis of an array of cDNAs including some that were full length. The initiation of polymerization was rate limiting: once synthesis had begun, it required 1-1.5 min to transcribe globin mRNA. However, most primers that were elongated were aborted prematurely. Maximum synthesis of full-length cDNA required stoichiometric levels of enzyme and high triphosphate levels, but regardless of conditions, the sum of completed cDNA and deadenylated mRNA accounted for only 50% of the input mRNA. The data fit a model in which synthesis of full-length cDNA molecules depends on the arrangement of primers and transcription initiation complexes on the poly(A) "tail" of mRNA.

Animals↗
PubMed1982

Interferon enhancement of the invasive capacity of Ewing sarcoma cells in vitro.

The ability of interferons to reduce cell proliferation in vitro and in vivo is a well-studied phenomenon. To extend such observations, the effect of interferons on the invasiveness in vitro of human malignant cells derived from a Ewing sarcoma was evaluated. Two related parameters were examined: (i) production of type IV (basement membrane) collagenase and (ii) penetration of human amnion basement membrane and collagenous stroma. After 6 days of treatment with crude fibroblast, leukocyte, or lymphoblastoid interferon at 100 units/ml in serum-free medium, type IV collagenase levels increased 2- to 4-fold per cell relative to those of untreated controls. With homogeneous fibroblast and lymphoblastoid interferons, a 2-fold elevation in type IV collagenase was detected after 2 days, with further increases, occasionally dramatic, occurring on the 4th and 6th day of treatment. The ability of Ewing sarcoma cells to invade human amnion connective tissue was measured after 6 days of treatment with various interferons. Relative to the behavior of untreated controls, crude leukocyte interferon, homogeneous lymphoblastoid interferon, and homogeneous fibroblast interferon at 100 units/ml augmented invasiveness 3-, 17- and 22-fold, respectively, when cells were allowed 4 days in which to traverse the amnion. When untreated cells were exposed simultaneously to the amnion and to homogeneous lymphoblastoid or fibroblast interferon, a 4- to 5-fold increase in invasiveness above control levels was observed in 2 days. These data emphasize the complexity of interferon-induced phenomena. In any overview, the effects of interferon on both the tumor cell and the host must be considered.

Amnion↗
PubMed1982

Sympathetic orchiopathia--an experimental and clinical study.

An experimental and a clinical study have been performed to elucidate the nature of contralateral testicular damage following unilateral testicular injury--sympathetic orchiopathia. In an experimental study significant impairment of sperm production was produced by contralateral testicular damage which did not seem to be immunologically mediated or to involve the breakdown of the "blood-testis" barrier. In 5 subfertile patients with oligozoospermia and unilateral testicular damage, removal of the damaged testicle did not result in an improvement in their semen analysis.

Animals↗
PubMed1982

The diagnosis of unilateral testicular obstruction in subfertile males.

Thirty-two subfertile males with sperms in the ejaculate and unilateral testicular obstruction are reported: the diagnosis was established by exploration of scrotum in 26, clinically in 2, 3 had had previous partially successful epididymovasostomies, and 1 had had an epispadias repair. The past medical history gave relevant information in 27 (84%), and useful findings were made on clinical examination in a further 3 cases. Fifteen patients had sperm counts over 20 million per ml, and 15 were less than 10 million per ml. Twenty-six (81%) had serum antisperm antibodies detected by tray agglutination test (TAT), 21 (81%) of whom had evidence of head-to-head (HH) agglutinins in pure or mixed form. Comparison with 162 vasectomised males and 160 naturally infertile males with antisperm antibodies showed that 55% of the former and 24% of the latter had HH agglutinins on TAT, differences that were highly significant on statistical analysis. Evidence of obstruction was found in 14 (37%) of 38 naturally infertile males with antisperm antibodies and HH or mixed agglutination, but only in 12 (10%) of 122 with TT agglutinins: this difference was also highly significant. Clinical history, physical examination and serum antisperm antibodies, especially if HH agglutinins are present, can suggest the possibility of unilateral testicular obstruction, but confirmation of the diagnosis requires exploration of scrotum.

Agglutination Tests↗