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Biomedical subjects

P R Wilkes

Publications and source records attributed to P R Wilkes.

15 recordsLinked to original sources
PubMed1994

Bain circuit occluded by foreign body.

The purpose of this report is to describe a potentially hypoxic event which occurred during mask induction with the Bain circuit in a healthy. ASA I boy. Failure of induction occurred because a pop-off weight from a bubble bottle was lodged in the elbow connecting the Bain circuit to the mask and prevented gas flow. Pethick and Foëx-Crampton Smith tests of the Bain circuit could also have missed this condition. Such an anaesthetic mishap could occur with any breathing circuit which is re-used. Although there was no serious misadventure, the potential for an hypoxic complication with either intra-venous induction of anaesthesia, or dislodging of the weight into the airway was significant. We conclude that the standard tests of system patency do not ensure safety.

Anesthesia, Closed-Circuit↗
PubMed1994

Reevaluation of the balloon in gastrointestinal manometry.

Although the flow-through catheter (FTC) system has been useful and satisfactorily accurate for gastrointestinal manometry, we hypothesized that a cylindrical, liquid-filled balloon would also accurately reflect stress imposed by a sphincter. Latex balloons were fitted over the side ports of a closed-end catheter. The responses of the balloon and FTC system were compared in a cylindrical chamber commonly identified as a Starling resistor. Independent, constant-pressure sources were used to control both the inwardly directed "contact pressure" of the Starling resistor (Ps) and the intraluminal fluid pressure (P(lum)). The balloon transducers responded linearly and accurately (slope = 1) to changes in both Ps and P(lum) within the test range (0-200 mmHg, 0-26.7 kPa). When either P(lum) or Ps was held constant and the other changed, the balloon transducers always accurately measured the higher of the two pressures. Although the performance of the FTC system was improved after the Starling resistor was lubricated, the FTC system sometimes responded inaccurately to changes in Ps. The ability of the balloon transducers to measure the contractions of the lower esophageal sphincter and of the esophagus was demonstrated. We conclude that the balloon transducer can measure sphincter pressure accurately and suggest that, in certain circumstances, it might be advantageous relative to the FTC system.

Digestive System Physiological Phenomena↗
PubMed1989

Pericardial pressure attenuates release of atriopeptin in volume-expanded dogs.

The role of the pericardium in the release of atriopeptin (AP) was examined, utilizing two separate protocols, in alpha-chloralose-anesthetized dogs. Protocol I consisted of an experimental group (9 dogs), in which the pericardium was incised to allow instrumentation and reapproximated, and a control group (6 dogs), in which the pericardium was left undisturbed. In the experimental group, mean right atrial pressure (Pra) was elevated from a control value of 1.8 +/- 0.9 mmHg (mean +/- SD) to 8.3 +/- 0.8 mmHg for 40 min by volume expansion with isoncotic, lactated Ringer solution. After this period of volume expansion, the pericardium was removed while holding Pra at 8 mmHg. During volume expansion, arterial blood samples for AP analysis were taken at 5, 10, 15, 20, 30, and 40 min, pre- and postpericardiectomy. A similar protocol was followed in the control group. At a Pra of 8 mmHg prepericardiectomy, the plasma AP concentration was 76 +/- 17 pM/l and 74 +/- 38 pM/l in the experimental and control groups, respectively. However, after pericardiectomy, AP levels increased significantly in both the experimental group (136 +/- 41 pM/l; P less than 0.001) and the control group (107 +/- 53 pM/l; P less than 0.025). In protocol II (6 dogs), the pericardium was removed before volume expansion, and Pra was elevated by 2- to 3-mmHg increments and maintained for periods of 13 min at each pressure. AP concentration did not increase until Pra reached 3-4 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Acid-base regulation during exercise and recovery in the blue crab, Callinectes sapidus.

During swimming activity Callinectes sapidus incurred a severe hemolymph acidosis due to elevated levels of PCO2 and lactate. Although hemolymph lactate concentration rose steadily during 1 h of exercise, hemolymph pH was maximally depressed within the first 15 min. A discrepancy between the quantities of lactate and H+ released from the tissues into the hemolymph is explained by a large apparent efflux of H+ into the ambient seawater, presumably via a branchial ion exchange process. Ammonia excretion increased 6 fold during exercise, but it is not clear if this contributed to the excretion of H+. The total quantity of H+ excreted into the environment during exercise and recovery far exceeded that which could be attributed to hemolymph lactic acid, indicating that some of the excreted H+ must have originated from other sources, such lactic acid which dissociated intracellularly, with the lactate anions remaining in the cells. Because lactate anions increase hemocyanin O2 affinity when unopposed by the Bohr shift, the excretion of a large portion of the metabolic H+ load, leaving lactate behind in the hemolymph, has important consequences for the regulation of O2 transport during swimming.

Acid-Base Equilibrium↗
PubMed1982

Regulation of the relative abundances of mRNAs in hepatoma and liver.

Comparison of the polysomal poly(A)+ RNAs of normal rat liver and hepatoma (HTC) cells have shown that, while few sequences are specific to either hepatocytes or hepatoma cells, some of the abundant liver mRNAs (perhaps 20% by weight) are much rarer in the polysomal RNA from HTC cells. In contrast, these mRNA sequences are at quite similar abundances in nuclear poly(A)+ RNA from hepatocytes and hepatoma cells. The use of cloned cDNAs to measure the relative abundances of individual liver mRNA sequences in hepatocytes and HTC cells has shown that these changes occur in both directions, and indicated that post-transcriptional modulations, which are cell-type-specific and sequence-specific, play a significant role in establishing steady-state levels of polysomal poly(A)+ mRNAs. To investigate post-transcriptional regulation of mRNA abundance, a cell-free system consisting of isolated HTC-cell nuclei has been developed. This system supports the in vitro processing and/or transport of rRNA and a complex mixture of poly(A)+ RNA sequences which resembles polysomal poly(A)+ RNA from HTC cells. The pattern of relative abundances of the sequences in released poly(A)+ RNA is intermediate between that of polysomal and nuclear poly(A)+ RNAs, and indicates that some degree of sequence-specific selection of processing and/or transport is maintained in isolated nuclei. Sequence-specific selection of individual poly(A)+ RNA sequences in vitro has been detected with cloned cDNAs.

Animals↗
PubMed1982

H+ excretion in the marine teleost Parophrys vetulus.

This study examined the branchial, renal and blood acid-base responses of a marine teleost to intravascular infusion of mineral acid (HCl at 1000 mu-equiv/kg). In all animals the renal response was insignificant for at least 3 days following infusion. Two types of branchial and blood acid-base response were seen. Either the infused load disappeared rapidly from the extracellular into the intracellular compartment and was slowly cleared from the body (+ 16 h following infusion) or, more commonly, remained in the extracellular compartment until rapidly cleared by a pronounced increase in branchial excretion. In the latter the amount excreted exceeded that infused by about twofold on average. These responses are discussed in relation to those of freshwater teleosts.

Acid-Base Equilibrium↗
PubMed1981

The appearance of new polyadenylated nuclear RNA sequences during rat-liver regeneration.

Polyadenylated RNA populations from normal and 16-hour regenerating rat-liver nuclei were compared by heterologous hybridisation reactions with cDNA and unique DNA probes. Whereas unique DNA hybridisations did not show differences between the RNA populations, comparisons by cDNA hybridisation showed that about 10--15% by weight of polyadenylated sequences present in the nuclei of 16-hour regenerating rat livers were not found in the polyadenylated nuclear RNA of normal rat livers. These regenerating-specific nuclear cDNA sequences were isolated and characterised; the experiments showed that the complexity of the new sequences was 1-2 x 10(7) nucleotides (equivalent to 5,000--10,000 RNA sequences of 2,000 nucleotides in length) and that they were probably not potential messenger RNA sequences.

Animals↗
PubMed1981

Reproductive anatomy and cytogenetics of freemartin heifers.

Out of a batch of 46 heifers obtained for breeding 19 were found to be freemartins by both anatomical and cytogenetic examination. Considerable variation existed in the reproductive tracts of these freemartins from structures that were essentially female to some that were essentially male in type. One heifer had a functional ovary containing a corpus luteum and had shown signs of oestrus. Sex chromosome chimaerism was detected in cultured leucocytes and in bone marrow from each of the freemartins, ranging from 2 per cent to 96 per cent male cells. Chimaerism was also detected in cell cultures from spleen, lung and gonad but at very low levels (less than 2 per cent male cells). None of the freemartins consistently showed the presence of male cells in all organs cultured. The problem of the clinical diagnosis of freemartins is discussed in relation to these results.

Animals↗
PubMed1980

A new operational approach to PCO2 determination in crustacean hemolymph.

A new method of calculating PCO2 based on mathematical expressions derived from a measured 'Davenport diagram' is described. The measured 'Davenport diagram' is constructed from in vitro buffer curves relating total CO2 to pH at PCO2 levels which adequately encompass the in vivo range of the acid-base status for the species in question. The 'Davenport diagram' is described by three linear equations such that PCO2 can be accurately calculated from in vivo measured CCO2 and pH. The equations are specific for a given species at a given temperature and hemolymph ionic strength, as are the constants in the more classical Henderson-Hasselbalch equation. The accuracy of the method is equal to calculations using the Henderson-Hasselbalch equation with corrected values for pK1' and alpha CO2 and in vivo PCO2 measured directly. This procedure is equally applicable to fluids with dissolved pigments such as hemolymph from freshwater and marine crustaceans and to human blood. The major benefit of this method of calculating PCO2 is that correction nomograms for the constants in the Henderson-Hasselbalch equation are not required.

Acid-Base Equilibrium↗
PubMed1980

Non-equilibrium acid-base status in C. productus: role of exoskeletal carbonate buffers.

Hemolymph acid-base variables (pH, PCO2 and CCO2), hemolymph Ca2+ and Na+ concentrations, and osmolality were measured in unrestrained crabs, Cancer productus, before, during and following 4 hr emersion and 43 hr hyperoxia (460-510 Torr), both at 10 degrees C. Emersion and hyperoxia provoked an acidosis associated with elevation of hemolymph CCO2 and PCO2, yet attempts to calculate PCO2 from measured pH and CCO2 always resulted in values greater than those measured directly. This discrepancy between measured and calculated PCO2, was associated with base excess, and was eliminated upon in vitro equilibration of the hemolymph and more slowly in vivo, suggesting that metabolic compensation for the acidosis occurred more rapidly than could acid-base equilibration. During emersion, increases of CCO2 and [Ca2+] provide evidence that the internal CaCO3 stores, possibly from the exoskeleton, were mobilized during acid-base compensation. Hyperoxia provoked no such increase in Ca2+, and branchial uptake of HCO3- may make a major contribution to the elevation of CCO2 during hyperoxia. It is suggested that shell buffering by aquatic crustaceans provides a means of compensation for acidosis under conditions during which branchial function is impaired.

Acid-Base Equilibrium↗
PubMed1979

Changes in nuclear and polysomal polyadenylated RNA sequences during rat-liver regeneration.

Nuclear and polysomal polyadenylated RNA populations of normal and 16 hour regenerating rat liver have been compared by mRNA-cDNA hybridisations and by unique DNA saturation experiments. It was found that nuclear polyadenylated RNA hybridises to 6.8% of unique DNA in both normal and 16 hour regenerating rat liver. However, cross-hybridisation experiments using cDNA have shown that 10-15% by weight of nuclear polyadenylated RNA sequences are specific to 16 hour regenerating rat-liver. Since both unique DNA and cDNA hybridisation have shown that normal and 16 hour regenerating rat-liver polysomal polyadenylated RNA populations are qualitatively very similar sequences specific to 16 hour regenerating rat-liver nuclear polyadenylated RNA are nucleus confined. Polysomal RNA sequences which were abundant in normal rat-liver have become less abundant in regenerating rat liver.

Animals↗
PubMed1978

Studies on a sheep freemartin.

A case of intersexuality in a Dorset horn ewe is described. Although possessing female external genitalia this animal had a male internal reproductive tract with inguinal testes, epididymes, vasa deferentia and seminal vesicles. No traces of cervix or uterus were present and the vagina was represented in its caudal part only. Chromosomal studies revealed chimaerism in peripheral leucocytes of the type 54, XX/54, XY, while other tissues revealed the normal female karyotype 54, XX. The ewe was born in a set of triplets with one dead male fetus and one living male. It was therefore concluded that the animal was a freemartin. The significance of this case and of the phenomenon of freemartisism in sheep is discussed.

Animals↗
PubMed1977

Heifer sterility associated with single-birth freemartinism.

Thirty-four heifers not conceiving to three or more inseminations or natural service were bled and karyotyped by leucocyte culture. Twelve were found to be sex-chromosome chimeras of which five were single-born. Three out of the five singleton sex-chromosome chimeric heifers were slaughtered and at post mortem examination abnormalities of the reproductive tract were observed. Two the the slaughtered animals were Friesian heifers that had shown normal oestrous cycles and had reproductive organs apparently normal on clinical examination; however, one of them with 5 per cent male cells had a nonpatent cervix, while the other with 12 per cent male cells had non-patent uterine horns. Both heifers possessed functional ovaries, the former had an active corpus luteum and the latter had a developing follicle. The third heifer with 45 per cent male cells had a normal vagina, enlarged clitoris, seminal vesicles and gonads resembling fetal testes with both primitive ovarian and testicular structures. The Old Gloucester and Friesian heifers with 2-5 per cent and 12-0 per cent male cells are alive and have normal external genitalia but rudimentary uterine horns with no palpable gonads. Cytogenetic examination has demonstrated for the first time the existence of single-born freemartins resulting from the death of their male co-twins after fetal vascular anastomosis has been established.

Animals↗