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Biomedical subjects

M W Miller

Publications and source records attributed to M W Miller.

At least 361 records · Page 20Linked to original sources
PubMed1962

Successive Microbial Populations in Calimyrna Figs.

Smyrna-type (Calimyrna) figs have essentially sterile internal tissue until visited by the pollinating fig wasp, Blastophaga psenes, which introduces a specific microflora consisting of Candida guilliermondii var. carpophila and Serratia plymuthica. This flora persists and develops in numbers throughout the ripening period until maturity of the fruit. These organisms do not cause spoilage. The presence of C. guilliermondii var. carpophila appears to increase the attractiveness of the fruit to drosophilae. Drosophila (mainly D. melanogaster) carry spoilage yeasts and bacteria on their exterior body parts, and introduce these organisms during ovipositing in the fruit cavity. The spoilage yeasts consist almost entirely of apiculate yeasts (Hanseniaspora valbyensis, H. uvarum, and Kloeckera apiculata) and of Torulopsis stellata, which cause active fermentative spoilage. Spoilage bacteria (primarily Acetobacter melanogenus) are also introduced with the yeasts. Organic acids are produced by these yeasts as well as by the Acetobacter. A number of minor spoilage yeasts were also identified.

Journal Article↗
PubMedDate not supplied

The effects of continuous wave and pulsed ultrasound on rat thymocytes in vitro.

Rat thymocytes in suspension were exposed to continuous wave and pulsed ultrasound at frequencies of 0.5 and 1 MHz. In qualitative confirmation of the observations of Chapman et al. (1979), cell lysis and cell survival were found to depend upon ultrasound intensity, frequency and time of exposure. Cell survival after 10 min, 2 W/cm2, 0.5 MHz was approx. 40 percent of control. Pulsed exposures at 0.5 MHz with the same temporal average intensity but with a temporal peak intensity of 30 W/cm2 showed no statistically significant decrease in survival in comparison with controls. The thymocyte observations provide no support for the belief that diagnostic ultrasound may cause biological effects in the fluids of the body.

Animals↗
PubMedDate not supplied

The kinetics and mechanics of ultrasonically-induced cell lysis produced by non-trapped bubbles in a rotating culture tube.

The kinetics of ultrasonically-induced cell lysis are examined in terms of classical radiation biology target theory. A theoretical expression relating the concentration of intact cells remaining after a given period of sonication in a rotating culture tube to the number of non-trapped bubbles, l, which a cell must encounter in order to be lysed is obtained. The expression is compared to experimental results in order to determine the actual value of l. It is found that l equals one (1). The concentration of non-trapped bubbles which is responsible for the observed cell lysis is calculated to be 250-500 cm-3. Finally, it is proposed that non-trapped bubbles tunnel into cells while undergoing stable cavitation and that cell lysis is produced by one or more transient events inside the cell.

Animals↗
PubMedDate not supplied

Lack of ultrasound effect on in vitro human lymphocyte sister chromatid exchange.

The frequency of sister chromatid exchanges (SCEs) in human lymphocytes cultured in vitro was not affected by a 30 min exposure to a 2.25 MHz focused ultrasound beam (from a clinical diagnostic unit with a pulse repetition rate of 1000 Hz, a 1 mu sec burst duration, and a 2-200 W/cm2 maximum intensity). A 30 sec exposure to continuous wave 1 MHz 2 W/cm2 (SP) ultrasound from an experimental device lysed 10-15% of the lymphocytes; there was no increase in SCEs in the survivors relative to unexposed controls. Treatment of lymphocytes with 0.033 micrograms/ml mitomycin-C, a known SCE inducer, increased the frequency of SCEs about 4 times above control levels.

Cells, Cultured↗
PubMedDate not supplied

Lack of effect of high-intensity pulsed ultrasound on sister chromatid exchange and in vitro Chinese hamster ovary cell viability.

The frequency of sister chromatid exchanges (SCEs) in in vitro Chinese hamster ovary cells and their viability were not affected by 3-min exposures to 2-4 MHz, focused, pulsed ultrasound with a pulse repetition rate of 200 Hz, pulse duration of 10 mu sec and intensities (SPTP) of 500 W/cm2 and 2500 W/cm2. The viability results are consistent with those reported elsewhere; the SCE response does not verify a specific previously reported positive response.

Animals↗
PubMedDate not supplied

Collateral circulation in experimental coarctation of the aorta in minipigs: a possible association with hypertrophied vasa vasorum.

Experimental coarctation of the thoracic aorta was produced in 13 adult Yucatan minipigs by placing a gradually expanding "C-shaped" occluder around the aorta. The aortic constriction was standardized by measuring the blood pressure above the coarctation, with a mean arterial pressure of 165-170mmHg as the target. The pigs were humanely killed after 8 weeks of hypertension. No deaths were associated with constriction of the aorta, and neither rear limb weakness nor neurological dysfunction was noted. The lack of clinical signs in these animals suggested the development of an extensive collateral circulation. Collateral vessels, which were verified angiographically, included intercostal arteries, muscular intercostal arteries, and the internal thoracic artery. In two of the animals in which the thoracic aorta was completely occluded, revascularization also occurred via small arterial channels. Histologically, there was a marked increase in the number of vessels as well as significant hyperplasia and hypertrophy of smooth muscle of adventitial vasa vasorum. These findings support the hypothesis that collateralization of occluded thoracic aortas may be aided by hypertrophy of the vasa vasorum. To our knowledge, these vessels have not previously been shown convincingly by histopathological methods to revascularize occluded large arteries such as the aorta.

Angiography↗
PubMedDate not supplied

Hyperthermic teratogenicity, thermal dose and diagnostic ultrasound during pregnancy: implications of new standards on tissue heating.

Hyperthermia is a recognized teratogen in mammalian laboratory animals and is a suspected teratogen for humans. The purpose of this synopsis is to reanalyse existing data on hyperthermia-induced teratogenic effects in experimental mammalian systems in terms of a thermal dose (temperature:time) concept, and then to illustrate the utility of this concept to human situations involving potential thermal increments to post-implantation embryos and foetuses. For example, the threshold temperature elevation for hyperthermia-induced teratogenic effects in experimental mammals is estimated (but not rigorously tested) to be approximately 1.5 degrees C above core values for exposures of long duration, possibly with a thermal dose of approximately 5 min duration or more at 4 degrees C. This level of tissue temperature increment is within the capability of some modern diagnostic ultrasound (DUS) devices sold within the USA and abroad. Epidemiological studies have not indicated any hazard from the use of DUS, but such studies are limited in sensitivity and were conducted with DUS devices whose acoustic outputs were relatively low compared to those presently available. After a regulatory change that allowed for substantially increased acoustic outputs, modern DUS devices were mandated to provide the user with on-screen information (the Thermal Index, or 'TI') about ultrasound-induced temperature increments in the target tissue. The TI is generally accurate to within a factor of 2, but the factor may be as high as 6 in certain obstetric settings. Thus, informed use of and attention to the TI is strongly advised, with this admonition gaining increased emphasis if the present regulations regarding allowable acoustic outputs of DUS devices were to be further relaxed or eliminated.

Animals↗
PubMedDate not supplied

A canine model of multiple portosystemic shunting.

The objective of this study was to develop and describe an experimental canine model of multiple acquired portosystemic shunts (PSS) similar in nature to spontaneously occurring PSS. Sixteen dogs were used and were divided into a control (n = 6) and a diseased group (n = 10). Dogs of the diseased group were administered dimethylnitrosamine (2 mg/kg of body weight, po) twice weekly, and clinicopathologic, ultrasonographic, and hepatic scintigraphic findings were recorded during the development of hepatic disease and PSS. Surgery was then performed to permit visual verification of multiple shunts, catheter placement for portography examination, and biopsy of the liver. All diseased dogs developed severe hepatic disease and multiple PSS as documented visually at surgery and on portography. Based on this study, dimethylnitrosamine-induced portosystemic shunting appears to be an appropriate model for spontaneously occurring multiple PSS secondary to portal hypertension.

Animals↗
PubMedDate not supplied

Migration of peptide-immunoreactive local circuit neurons to rat cingulate cortex.

The times of origin of neurons immunoreactive for somatostatin (SRIF), cholecystokinin (CCK), and vasoactive intestinal polypeptide (VIP) were determined using a combined immunohistochemical-autoradiographic technique. 3H-thymidine (3H-dT) was injected into pregnant rats on gestational day 13 (G13), G15, G17, G19, or G21. Animals were killed on postnatal day 30, that is, after the completion of neuronal migration. Sections of the brain including posterior cingulate cortex (area 29), visual cortex (area 17), and somatosensory cortex (area 3) were processed serially for peptide immunoreactivity and autoradiographically for labeling with 3H-dT. SRIF- and CCK-immunoreactive neurons were cogenerated and comigrated according to an inside-to-outside sequence. Accordingly, neurons in layer VI were born on G13, neurons in intermediate layers were born on G15-G17, and neurons in layer II/III were born on G19-G21. In contrast, VIP-positive neurons did not follow such a sequence. Neurons in all layers of cortex were generated at relatively constant rates between G13 and G21. VIP-immunoreactive neurons were the only known subpopulation of neurons that did not migrate into cortex by an inside-to-outside sequence. Thus, the migration of local circuit neurons to cingulate cortex follows patterns that are similar to those discerned in more differentiated cortical areas.

Animals↗
PubMedDate not supplied

Complications common to ventricular assist device support are rare with 90 days of DeBakey VAD support in calves.

The DeBakey VAD is a miniaturized, electromagnetically driven axial flow pump intended for long-term ventricular assist. Safety and performance data from six calves implanted with the complete DeBakey VAD system are reported elsewhere; here we describe complications and necropsy findings for these same six animals, all of which survived 90 days. The study was conducted according to a uniform protocol, which included anticoagulation and antibiotic prophylaxis. Clinical complications tracked included bleeding, cardiovascular abnormalities (e.g., arrhythmias, tachycardia unrelated to pain, bradycardia), hemolysis, hepatic dysfunction, renal dysfunction, thromboembolism (neurologic or peripheral), or infection. Each adverse event was retrospectively categorized with regard to severity (mild, moderate, severe) and relationship to device. Clinical findings were confirmed by necropsy. There was no evidence of systemic infection, thromboembolism, hemolysis, or renal or hepatic dysfunction in these six animals during the study period. A single adverse event was noted in each of two of the calves. Both events were considered mild according to the predefined criteria. Bleeding related to the surgical implantation procedure and requiring reoperation occurred in one animal. The other animal had evidence of a superficial infection at the exit site of the cables on the left lateral thoracic wall; the infection did not extend into the thoracic cavity. Chronic, healed small renal infarct scars were present in several animals. Mild valvular endocardiosis was observed in two calves and mild fibroelastosis was present in the endocardium at the site of the inflow cannula in three calves; however, these lesions were not considered clinically significant. No other gross or histologic abnormalities were noted at necropsy. In conclusion, calves implanted with the complete DeBakey VAD for 90 days demonstrated few complications and had no significant necropsy findings. Complications common to ventricular assist device (VAD) support (i.e., hemolysis, infection, bleeding, thromboembolism) were rare during long-term support (90 days) with the DeBakey VAD.

Animals↗
PubMedDate not supplied

Lymphedema. Clinical signs, diagnosis, and treatment.

Medical management of lymphedema is warranted in all dogs with suspected congenital lymphedema, before surgical intervention. Although pharmaceutical agents, such as the benzo-pyrones, have not been investigated for clinical use in dogs, such studies appear to be justified. None of the surgical techniques discussed will cure lymphedema. The only technique reported with any frequency in the dog has been excision of affected tissues, and although some successes have been reported with this procedure, others have found it to be of no benefit or severe complications have occurred. Excisional techniques require meticulous attention to prevent infection intraoperatively and postoperatively. Staging the procedure may decrease problems associated with devascularization of remaining tissues. Evaluation of other techniques may be warranted in dogs; however, no technique has proven to be consistently beneficial in human beings with lymphedema.

Animals↗
PubMedDate not supplied

Familial ventricular arrhythmias in boxers.

The purposes of this study were to evaluate families of Boxers with ventricular arrhythmias to determine whether this disorder is a familial trait and, if so, to determine the mode of inheritance. Eighty-two Boxers were evaluated by physical examination, electrocardiogram, echocardiogram, and 24-hour ambulatory electrocardiogram. Dogs were considered affected if at least 50 premature ventricular complexes (PVCs) were observed during a 24-hour period. All dogs were at least 6 years of age at evaluation. Complete cardiovascular examinations were performed on dogs from 6 extended families. The 2 most complete pedigrees were used to determine the pattern of inheritance. The number of PVCs observed during a 24-hour period in affected dogs ranged from 112 to 4,894 (mean +/- SD, median; 1,309 +/- 2,609, 1,017). The number of PVCs observed during a 24-hour period in the unaffected dogs ranged from 0 to 16 (7 +/- 10, 12). Pedigree evaluation was performed to determine pattern of inheritance. An autosomal dominant pattern was determined to be most likely because a sex predisposition was not observed, affected individuals were observed in every generation, and 2 affected individuals produced unaffected offspring. We conclude that familial ventricular arrhythmias is inherited as an autosomal dominant trait in some Boxers.

Animals↗
PubMedDate not supplied

Comparison of the indirect oscillometric and direct arterial methods for blood pressure measurements in anesthetized dogs.

The indirect oscillometric method of blood pressure measurement was compared to the direct arterial puncture method in 15 anesthetized dogs, divided into three weight groups, undergoing a variety of surgical procedures. The objectives of this study were to determine the accuracy of the indirect oscillometric method at a single point in time and when sequential values were averaged. Additionally, the ability to detect systemic hypotension (i.e., mean systemic arterial pressure less than 60 mmHg) was evaluated. The method had the highest correlation coefficient (r of 0.8) when five sequential values were averaged and compared, and it appeared to be sensitive (100%) and specific (91%) for detecting hypotension.

Animals↗