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Biomedical subjects

L Heller

Publications and source records attributed to L Heller.

At least 19 recordsLinked to original sources
PubMed1992

Saccharomyces cerevisiae sec59 cells are deficient in dolichol kinase activity.

The temperature-sensitive Saccharomyces cerevisiae mutant sec59 accumulates inactive and incompletely glycosylated protein precursors in its endoplasmic reticulum at the restrictive temperature. O-mannosylation and glycosyl phosphatidylinositol membrane anchoring of protein are also abolished, consistent with a deficiency in dolichyl phosphate mannose. Membranes prepared from sec59 cells that had been shifted to the restrictive temperature, however, made normal amounts of dolichyl phosphate mannose when exogenous dolichyl phosphate was supplied, but dolichyl phosphate mannose synthesis was severely depressed in the absence of exogenous dolichyl phosphate. Quantitative measurements of dolichyl phosphate in sec59 cells showed that the levels were decreased to 48% of wild type at the permissive temperature and to less than 10% at the restrictive temperature. Assays of enzymes from the dolichyl phosphate synthetic pathway, cis-prenyltransferase and dolichyl pyrophosphate phosphatase, gave wild-type levels. However, dolichol kinase activity was greatly decreased. When sec59 cells were transformed with a plasmid that overexpresses the wild-type gene, dolichol kinase activity increased 10-fold over wild-type levels. These results strongly suggest that the sec59 gene encodes dolichol kinase.

Dimethylallyltranstransferase↗
PubMed1992

Brain stimulation using electromagnetic sources: theoretical aspects.

We prove that, at the frequencies generally proposed for extracranial stimulation of the brain, it is not possible, using any superposition of external current sources, to produce a three-dimensional local maximum of the electric field strength inside the brain. The maximum always occurs on a boundary where the conductivity jumps in value. Nevertheless, it may be possible to achieve greater two-dimensional focusing and shaping of the electric field than is currently available. Towards this goal we have used the reciprocity theorem to present a uniform treatment of the electric field inside a conducting medium produced by a variety of sources: an external magnetic dipole (current loop), an external electric dipole (linear antenna), and surface and depth electrodes. This formulation makes use of the lead fields from magneto- and electroencephalography. For the special case of a system with spherically symmetric conductivity, we derive a simple analytic formula for the electric field due to an external magnetic dipole. This formula is independent of the conductivity profile and therefore embraces spherical models with any number of shells. This explains the "insensitivity" to the skull's conductivity that has been described in numerical studies. We also present analytic formulas for the electric field due to an electric dipole, and also surface and depth electrodes, for the case of a sphere of constant conductivity.

Biophysical Phenomena↗
PubMed1992

An open trial of vacuum penile tumescence: constriction therapy for neurological impotence.

Sexual dysfunction is a frequent result of traumatic and non traumatic neurological disorders, including spinal cord injury, stroke, traumatic brain injury and autonomic neuropathy (for example, as may be seen in patients with diabetes mellitus). Although many methods have been suggested for the treatment of some of these problems in male patients, most are invasive and have a substantial morbidity. This is the report of a pilot trial of vacuum tumescence constriction therapy for 30 patients with chronic neurological impotence. Seventeen of these patients, following sexual counselling and training, decided to purchase such a device. At follow up, a mean of 21 months, over 50% of those who had purchased the device were still actively using it. The frequency of coitus increased from 0.3/wk to 1.5/wk (t = -5.7; p less than 0.0001). No significant morbidity was reported by patients. Vacuum tumescence constriction therapy shows promise as a noninvasive method for the treatment of neurological impotence.

Adult↗
PubMed1992

Noninvasive treatment for erectile dysfunction in the neurogenically disabled population.

Erectile dysfunction is the most prevalent sexual dysfunction in neurogenically disabled men. Studies of rehabilitation patients indicate that the restoration of sexual functioning is considered an important priority. This article reports on a pilot study of vacuum tumescence constriction therapy as a noninvasive method for use by a population with traumatic or nontraumatic neurologic disorders such as spinal cord injury, stroke, multiple sclerosis, and diabetes mellitus. Of the 30 patients who participated in the study, 17 purchased the device and over 50% of them reported using the device on a long-term basis. Frequency of coitus increased from 0.3/wk to 1.5/wk. Included in the study are methods used by patients to integrate the device into their sex life, the role of the patient's partner in the decision to purchase the device, and the rate of partner satisfaction. There were no reports of substantial morbidity. Thus, this method shows promise as a noninvasive treatment for men who are moderately to severely neurogenically disabled.

Equipment and Supplies↗
PubMed1975

[Parenteral feeding. Biochemical and clinical findings during continuous long-term infusion of glucose, fructose, sorbitol and xylitol. 2. Clinical aspects, discussion and results].

Four groups of six volunteers were given continuous infusions of glucose, fructose, sorbitol and xylitol in a dosage of 0.25 g/kg body weight over 48 hours. All solutions were well tolerated provided that potassium was supplemented in sufficient amounts. During the first 12 hour period of xylitol infusion renal potassium loss was greater than during infusion of all other substrates. No substantial differences in the alterations of the other parameters were noted between glucose and glucose substitutes. The only exception was the rise in serum uric acid concentration during infusion of xylitol and of fructose, which was not noted during infusion of glucose or sorbitol. The concentration of serum bilirubin was elevated during infusion of all four substances. The decrease in serum free fatty acid concentration was equally caused by glucose, fructose, xylitol or sorbitol. The increase in serum triglyceride concentration was observed earlier during the infusion of glucose substitutes as compared to glucose. Blood glucose concentration was only elevated during infusion of glucose. In the post infusion period there was quick rise in fatty acid concentration after cessation of glucose infusion. This normalisation occurred more slowly after stopping fructose and particulary xylitol or sorbitol. These results have no indications for adverse effects of the continuous infusions of glucose or glucose substitutes.

Bilirubin↗
PubMed1975

Suitability of non-glucose-carbohydrates for parenteral nutrition.

Postoperative parenteral nutrition can only be optimally effective if the characteristics of post-traumatic metabolism are taken into account. Two main possibilities are discussed for the carbohydrate component of parenteral nutrition during this phase: glucose with high doses of insulin or non-glucose carbohydrates (sugar substitutes) possibly in a suitable combination with glucose. The risks as well as the technical and organisational problems involved in the use of them are discussed and the authors prefer the second of the two alternatives. Possible side effects of non-glucose carbohydrates are pointed out and it is shown how these can be avoided by observing dose guidelines. So far a combination of frucose : glucose : xylitol in a ratio of 2 : 1 :1 with a total dose of 0.50 g/kg/hour has been studied most thoroughly. This combination normalises the fat metabolism and improves glucose tolerance without requiring exogenous insulin. Experiences with this combination as well as individual non-glucose carbohydrates on operated patients have been given continuously for up to 7 days and in some cases even for several weeks. No side effects, no deviations from a steady state and no abnormal changes of the laboratory values occurred. The authors are of the opinion that non glucose carbohydrates are necessary if the facilities for frequent blood sugar controls are not available.

Adenine Nucleotides↗
PubMed1975

[Changes in serum electrolyte concentration and electrolyte excretion induced through infusion of glucose or glucose-exchange substances].

The metabolic effects of intravenous infusion of glucose, fructose, sorbitol or xylitol were investigated using human volunteers. The infusion period was 4 hours or 48 hours. Serum phosphate concentration decreased quickly and independent on the kind of the carbohydrate used. On the other hand, the serum concentration of potassium or sodium did not show any greater deviations from normal. Considering the renal excretion, greater differences between the single substances were seen. Renal potassium excretion was increased especially during xylitol infusions, and not as much during sorbitol infusions, as compared to infusions with glucose or with fructose. These differences were demonstrated especially for the first 12 hours of the infusions periond. During the infusions of glucose or of fructose an oral substitution of the electrolytes was suggicient. However, during xylitol infusions an intravenous substitution of potassium salts was necessary, despite the fact that the changes in serum concentration were only small. It is emphasized to carefully monitor serum electrolyte concentration and renal electrolyte excretion during long lasting intravenous infusions therapy.

Electrolytes↗
PubMed1975

The Mitchell distal metatarsal osteotomy in the treatment of hallux valgus.

Many of the fair and poor results are directly traceable to errors in technique. Patient selection is also important. The operation can be done in adolescents since there is no growth plate at the distal end of the first metatarsal. We do not currently recommend this procedure for those over 60, for those with first metatarsophalangeal osteoarthritis or hallux rigidus or for those with moderate or severe rheumatoid arthritis. For these patients we usually do a Keller excisional arthroplasty. Our use of the osteotomy-bunionectomy operation for the patient with hallux valgus with an associated metatarsalgia or short first metatarsal has now become more cautious. We feel that the operation is not indicated for those with significant preoperative metatarsalgia, especially if the first metatarsal is shorter than the second, or for those whose first metatarsal is more than 4 or 5 millimeters shorter than the second, regardless of preoperative metatarsalgia. In these patients a McBride procedure or a proximal opening-wedge osteotomy is done.

Adolescent↗
PubMed1975

[Changes in serum electrolyte concentration and in urinary electrolyte excretion during the infusion of glucose or glucose substitutes].

In groups of volunteers the concentration differences of phosphate potassium and sodium in serum were measured during 48-hour continuous infusion of glucose or glucose substitutes (fructose, sorbitol or xylitol). The dosage was 0.25 g/kg BW/hour. Additionally, the effect of fructose infusion in a dosage of 0.5 g/kg BW/hour was observed. Besides, the urinary excretion of sodium and of potassium was analysed. In contrast to short-term and high-dosed infusions of glucose or glucose substitutes, the phosphate concentration in serum was scarcely influenced. Only during high-dosed fructose infusion and during infusion of xylitol and sorbitol a small decrease in serum phosphate concentration was noticed. The effect of xylitol is pronounced. Additionally, the sodium concentration in serum was especially decreased during xylitol infusion. With regard to the sodium excretion - and less pronounced with regard to the potassium excretion - a gradual adaptation to the infusion of the electrolyte-free solution is observed. The excretion of the cations is more and more decreased. In particular the excretion of sodium and of potassium is very high in the initial period, i.e. in the course of the first twelve hours of the xylitol infusions. On the other hand, the potassium excretion is very low in the final period of the infusion of xylitol (during 36 hours up to 48 hours) in comparison to the other sugars.

Adult↗
PubMed1975

[Paraplacental feeding of the fetus].

Amino acids, intraamnially administered, disappear unexpectedly rapidly and relatively uniformly from the amniotic fluid. During a placental insufficiency and thus a simultaneously present intrauterine protein deficiency, the amino acid level in the amniotic fluid decreases especially rapidly whereas it remains practically unchanged for hours following death in utero. This observation suggests that the infused amino acids are utilized by the living fetus. This is supported by a decrease in the glucose concentration and an increase in the pyruvate of the amniotic fluid. According to the experiences obtained until now it seems reasonable to supply the fetus with vital substrates via the paraplacental route.

Adult↗