Theoretical and experimental evidence of extinction and coexistence of killer and sensitive strains of yeast grown as a mixed culture in water.

Theoretical and experimental evidences of extinction and coexistence during batch interaction of killer and sensitive strains of Saccharomyces cerevisiae grown as a mixed culture in pure water are provided. The experimental results show that in the limited nutrient conditions of growth in pure water, the killer yeast is subject to extinction when the initial concentration ratio of killer to sensitive yeast is 1:100. However, if the initial concentration ratio of killer to sensitive yeast is 1:1, both strains coexist. Substantial damped oscillations are associated with the growth process in the mixed culture. A new theoretical model that was originally developed for recovering the growth of single species in isolation is extended and applied to two species competing over a common ecological niche. The solutions of the model are shown to recover all the qualitative features captured in the experiments.

Recovery of an oscillatory mode of batch yeast growth in water for a pure culture.

New experiments that we conducted show an oscillatory mode of batch yeast growth in water, for a pure culture of the T206 strain of Saccharomyces cerevisiae. The oscillations are damped over time, allowing the cell concentration to stabilize at the stationary equilibrium. A new proposed model that includes the complete cell growth dynamics is introduced and showed to recover the experimental oscillatory results. In addition the proposed model recovers effects that are frequently encountered in experiments such as a "Lag Phase" as well as an inflection point in the "ln curve" of the cell concentration. The proposed model recovers also the Logistic Growth Curve as a special case. For purposes of providing some interesting contrast we present additional experimental as well as computational results for the growth of the VIN7 strain of S. cerevisiae in a 5% grape juice medium. The latter indicates even stronger oscillations during the growth process. In order to capture experimentally the oscillatory growth behavior, very frequent readings are required (every 15-30 min) and the measurement process needs to be extended to longer than usual periods (over 250 h).

Electron microscopy of the K2 killer effect of Saccharomyces cerevisiae T206 on a mesophilic wine yeast.

A mesophilic wine yeast, Saccharomyces cerevisiae CSIR Y217 K-R- was subjected to the K2 killer effect of Saccharomyces cerevisiae T206 K+R+ in a liquid grape medium. The lethal effect of the K2 mycoviral toxin was confirmed by methylene blue staining. Scanning electron microscopy of cells from challenge experiments revealed rippled cell surfaces, accompanied by cracks and pores, while those unaffected by the toxin, as in the control experiments, showed a smooth surface. Transmission electron microscopy revealed that the toxin damaged the cell wall structure and perturbed cytoplasmic membranes to a limited extent.

Primary leptomeningeal histiocytic lymphoma in a young child.

A 20-month-old boy had an 8-week history of vomiting, lethargy, generalized muscle weakness, and seizures. There was no history or clinical signs of an underlying systemic disease or an immunodeficiency. Cerebrospinal fluid (CSF) had 99 nucleated cells/cu mm, malignant cells, high protein and normal glucose. CT and MRI scans showed diffuse meningeal enhancement around the brain and spinal cord, but no parenchymal involvement. Biopsy of the leptomeninges showed malignant cells with marked nuclear pleomorphism and prominent clear to eosinophilic cytoplasm. The immunohistochemical studies were positive for histiocyte-macrophage markers and were negative with T and B cells, Ki-1, neural and glial cell antibodies. Multiple tests revealed no other site of disease. The patient died 3 months after onset of treatment despite intensive i.v. and intrathecal chemotherapy. We have not found any other reported case of primary histiocytic leptomeningeal lymphoma in a young child.

Accidental penetrating cervical cord injury in a young child.

A three-year-old child presented to our emergency department with a hemiparesis five days following the accidental laceration of her neck with a piece of glass. The laceration had been thought to be superficial when she was initially evaluated. When seen again three days following the injury because of right-sided weakness, computerized tomography of her head and neck was unrevealing. However, using high resolution magnetic resonance imaging (MRI) we were able to demonstrate a C1-2 cord contusion and an injury tract leading from the surface of the neck to this site. The unusual mechanism of injury and the underlying pathophysiology of this patient's presentation are reviewed. It is important for the emergency physician to be reminded that what appears to be a superficial laceration can sometimes be more serious. MRI should be considered in the evaluation of patients who have suffered penetrating trauma if the potential for spinal cord injury exists and especially when there are signs or symptoms suggesting spinal cord dysfunction.

Short report: octreotide in the treatment of external pancreatic fistulas.

The efficacy of the long-lasting somatostatin analogue, octreotide, in the treatment of high-output pancreatic fistulas was investigated in this prospective, open study. Sixteen patients with post-operative pancreatic fistulas were treated with subcutaneous injections of octreotide 0.1 mg b.d. The output of the fistulas before the somatostatin therapy ranged between 190 and 570 ml/day. The therapy was begun on average 17 days following the appearance of the fistula (range 4 to 35 days). The decrease in volume one day after initiation of therapy ranged from 26% to 69%. By the third day of treatment the fistula volume decreased to 0-45% of the initial output. The treatment resulted in the closure of 14 of the 16 fistulas; the time to closure ranging from 3 to 15 days. The results suggest that octreotide is a useful adjuvant agent in the treatment of an external pancreatic fistula.

Secretin provocation ultrasonography in the diagnosis of papillary obstruction in pancreas divisum.

The diagnostic value of secretin provoked abdominal ultrasound was studied on 34 patients with pancreas divisum and on 20 control subjects. The patients received a 1.0 unit/kg body weight dose of secretin. The degree of ductal expansion and the time required to return to the initial state were registered and these values were compared to the clinical diagnosis. The control subject's ductal diameters prior to secretin administration were 1 mm in all cases (maximum expansion 2 mm, return to the initial value within 10 minutes). The pancreas divisum patients could be placed in two groups based on their initial ductal diameter. Fourteen patients had initial ductal diameters of 2 mm or greater (A group mean +/- SD: 2.4 +/- 0.3) while 21 patients had an initial value of less than 2 mm (B group; 1.7 +/- 0.3). Following secretin administration the ductal diameter of the A group's patients increased on average +/- SD to 1.3 +/- 0.5 times the initial value and in the B group 3.2 +/- 1.1 times the initial value (p less than 0.01). In the A group the ductal diameter returned to it's initial value within 10 minutes while it took 35 minutes for the same to occur in the B group. A relationship can be observed between the clinical diagnosis, the initial ductal diameter, the degree of expansion following secretin administration and the time required to return to the initial state.

Intrapartum fetal vibratory acoustic stimulation during spontaneous and induced states of low activity and low heart rate variability.

Fetal response to vibratory acoustic stimulation (VAS) was studied in 12 healthy parturients in the active phase of labor. All fetuses were evaluated in both spontaneous and analgesia-induced states of low activity and low cardiac beat-to-beat variability. Analgesia was induced with intravenous maternal administration of meperidine, 0.8 mg/kg, plus a fixed dose of promethazine (25 mg). The vibratory acoustic stimulus was applied ten minutes after the start of a fetal quiet state, and ten minutes of fetal behavior was observed after application of the stimulus. The number and mean duration of fetal body movements in the unmedicated fetuses were statistically significantly higher than in the medicated group. Similarly, the number of fetal heart rate accelerations was significantly higher in the unmedicated fetuses than in the medicated ones. Ten minutes after VAS no fetus in the unmedicated group was in a quiet behavioral state, while 10 of 12 medicated fetuses (83%) returned to a quiet state.

Influence of the fetal scalp electrode stimulation test on fetal heart rate and body movements in quiet and active behavioral states during labor.

Thirty women were studied to examine the effect of fetal scalp stimulation on fetal heart rate (FHR) accelerations and gross body movements in quiet and active fetal behavioral states during the active phase of labor. Stimulation was performed by five consecutive tractions of the fetal scalp electrode. Fetal response in terms of fetal movements and FHR accelerations occurring within 15 seconds after stimulation was observed in all fetuses of the active state group. In the quiet state group 14 of 15 fetuses responded with body movements and in 12 fetuses FHR accelerations were observed. Subsequently, most of the fetuses returned to the quiet state. We suggest that a normal and healthy fetus is expected to respond to the fetal scalp electrode stimulation test even in the quiet behavioral state.

Influence of meperidine on fetal movements and heart rate beat-to-beat variability in the active phase of labor.

Eleven parturients were studied in the active phase of labor. Fetal movements, fetal heart rate, and short-term beat-to-beat variability as well as uterine contractions were evaluated for two 40-minute recording periods before and after maternal intravenous administration of 50 mg meperidine. Meperidine depressed fetal activity and increased the duration and frequency of uterine contractions. Fetal movements were significantly reduced from 156 to 60 and their relative duration from 8.6 +/- 6.0% to 2.4 +/- 2.6% (p less than 0.01). The short-term fetal heart rate beat-to-beat variability was reduced at the baseline period 5.22 +/- 1.02 versus 4.62 +/- 1.47 (p less than 0.05) but not during uterine contractions or fetal movements. The frequency of uterine contractions increased from 3.1 +/- 0.8 to 3.7 +/- 0.7 per 10 minutes (p less than 0.01), and their relative duration from 35.3 +/- 6.9% to 40.1 +/- 5.9% (p less than 0.05).

Development of a biopolymeric keratoprosthetic material. Evaluation in vitro and in vivo.

Based on the results of in vitro and in vivo experiments, we have determined that the optimal material for the central transparent portion of a perforating keratoprosthesis is a polyvinyl alcohol copolymer hydrogel. The material supports the maintenance and growth of corneal epithelium in vitro as shown by population doublings and transmission electron microscopy. Discs preseeded with epithelial cells were cultured in vitro and transplanted into rabbit corneas. The proliferation of these cells in vivo was demonstrated using 3H-thymidine. Other experiments showed that the preseeded cells not only migrated from the central disc onto the peripheral rim of the host cornea but also that host peripheral epithelial cells migrated onto the anterior surface of the disc. The experiments described in this paper demonstrate that corneal epithelial cells preseeded onto hydrogel discs and transplanted into rabbit corneas remain adherent and are capable of proliferating.

Association between fetal movements and uterine contractions in the active phase of labor.

Fetal body movements were studied for 40 minutes during the active phase of labor in 15 parturients. The total duration of fetal movements constituted 8.2% of the recording period, with a frequency of 3.8 +/- 2.1 per ten minutes. Of all the movements, 57.3% were associated with uterine contractions, while 40.7% of all uterine contractions were associated with fetal movements. All the fetuses moved in the first 30 minutes of the study period. The fetal movements that were associated with uterine contractions were longer than those not associated with contractions. Similarly, uterine contractions associated with fetal movements were longer than other uterine contractions.

Fetal heart rate beat-to-beat variability in uncomplicated labor.

18 healthy parturients were monitored during normal labor in order to determine the influence of uterine contractions and fetal body movements on fetal heart rate beat-to-beat variability (BTBV). The BTBV was 5.37 +/- 1.28 during the baseline period and a significant increase to 6.46 +/- 1.64 was found during uterine contractions (p less than 0.001). The BTBV during fetal movements, 6.21 +/- 2.29, did not differ significantly from the value of the baseline period.

The relationship between uterine contractions, fetal movements and fetal heart rate patterns in the active phase of labor.

The relationship between fetal movements, fetal heart rate and uterine contractions was studied with a computerized system in 18 parturients during the active phase of labor. 80% of FHR accelerations and 39% of uterine contractions were associated with fetal trunk movements. The probability of association was greater in longer movements and larger accelerations. 98% of fetal movements which lasted 10-15 s, 98% of accelerations with an amplitude of 25-30 bpm and 96.4% of accelerations with a duration of 40-50 s were associated with fetal trunk movements.