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Biomedical subjects

N Hirsch

Publications and source records attributed to N Hirsch.

At least 19 recordsLinked to original sources
PubMed2005

Lymphocyte contamination of laryngoscope blades--a possible vector for transmission of variant Creutzfeldt-Jakob disease.

Variant Creutzfeldt-Jakob disease (vCJD) is associated with extensive prion infection of lymphoreticular tissues during the prolonged asymptomatic incubation period. Instruments exposed to infected tissues of preclinically infected individuals during medical or surgical procedures represent a potential risk of iatrogenic transmission of vCJD prions. We assessed the frequency of contamination with lymphoid tissue of single-use laryngoscope blades used for tracheal intubation for general anaesthesia. Using a cyto-centrifugation technique, lymphocytes were detected from 30% of laryngoscope blades studied. As prions resist routine sterilisation procedures, the use of non-disposable laryngoscope blades poses a risk of transmitting vCJD from patient to patient. The use of such instruments should be abandoned and disposable alternatives used.

Anesthesia, General↗
PubMed2002

Outcome of ventilatory support for acute respiratory failure in motor neurone disease.

OBJECTIVES: To review the outcome of acute ventilatory support in patients presenting acutely with respiratory failure, either with an established diagnosis of motor neurone disease (MND) or with a clinical event where the diagnosis of MND has not yet been established. METHODS: Outcome was reviewed in 24 patients with respiratory failure due to MND who received endotracheal intubation and intermittent positive pressure ventilation either at presentation or as a result of the unexpected development of respiratory failure. Patients presenting to local hospitals with acute respiratory insufficiency and requiring tracheal intubation, ventilatory support, and admission to an intensive therapy unit (ITU) before transfer to a regional respiratory care unit were selected. Clinical features of presentation, management, and outcome were studied. RESULTS: 24 patients with MND were identified, all being intubated and ventilated acutely within hours of presentation. 17 patients (71%) were admitted in respiratory failure before the diagnosis of MND had been made; the remaining seven patients (29%) were already known to have MND but deteriorated rapidly such that intubation and ventilation were initiated acutely. Seven patients (29%) died on ITU (between seven and 54 days after admission). 17 patients (71%) were discharged from ITU. 16 patients (67%) received long term respiratory support and one patient required no respiratory support following tracheal extubation. The daily duration of support that was required increased gradually with time. CONCLUSION: When a patient with MND is ventilated acutely, with or without an established diagnosis, independence from the ventilator is rarely achieved. Almost all of these patients need long term ventilatory support and the degree of respiratory support increases with time as the disease progresses. The aim of management should be weaning the patient to the minimum support compatible with symptomatic relief and comfort. Respiratory failure should be anticipated in patients with MND when the diagnosis has been established.

Acute Disease↗
PubMed2000

The development of Xenopus tropicalis transgenic lines and their use in studying lens developmental timing in living embryos.

The generation of reporter lines for observing lens differentiation in vivo demonstrates a new strategy for embryological manipulation and allows us to address a long-standing question concerning the timing of the onset of differentiation. Xenopus tropicalis was used to make GFP reporter lines with (gamma)1-crystallin promoter elements directing GFP expression within the early lens. X. tropicalis is a close relative of X. laevis that shares the same ease of tissue manipulation with the added benefits of a diploid genome and faster life cycle. The efficiency of the Xenopus transgenic technique was improved in order to generate greater numbers of normal, adult transgenic animals and to facilitate in vivo analysis of the crystallin promoter. This transgene is transmitted through the germline, providing an accurate and consistent way to monitor lens differentiation. This line permitted us to distinguish models for how the onset of differentiation is controlled: by a process intrinsic to differentiating tissue or one dependent on external cues. This experiment would not have been feasible without the sensitivity and accuracy provided by the in vivo reporter. We find that, in specified lens ectoderm transplanted from neural tube stage donors to younger neural-plate-stage hosts, the onset of differentiation, as measured by expression of the crystallin/GFP transgene, is delayed by an average of 4.4 hours. When specified lens ectoderm is explanted into culture, the delay was an average of 16.3 hours relative to control embryos. These data suggest that the onset of differentiation in specified ectoderm can be altered by the environment and imply that this onset is normally controlled by external cues rather than by an intrinsic mechanism.

Animals↗
PubMed1998

Respiratory insufficiency due to high anterior cervical cord infarction.

OBJECTS AND METHODS: Respiratory dysfunction may occur as a result of lesions in the upper cervical spinal cord disturbing the descending pathways subserving automatic and volitional ventilatory control. Four patients are described who presented with acute respiratory insufficiency caused by infarction of the anterior portion of the upper cervical cord due to presumed anterior spinal artery occlusion. RESULTS: Two patients presented after respiratory arrests; they were ventilated and there was no automatic or volitional respiratory effort. Both had signs of an extensive anterior spinal cord lesion at the C2 level and this was confirmed by MRI. One patient presented with a C4 infarction and required ventilation for three months. Ventilatory recovery was characterised by the development of an automatic respiratory pattern. The fourth patient required ventilation for two months after infarction at the C3 level. On attempted weaning he had prolonged periods of hypoventilation and apnoea during inattention and sleep indicating impairment of automatic respiratory control. CONCLUSION: Infarction of the spinal cord at high cervical levels may be due to fibrocartilaginous embolism and involvement of the descending respiratory pathways may occur. Extensive lesions at C1/2 cause complete interruption of descending respiratory control leading to apnoea. Partial lesions at C3/4 cause selective interruption of automatic or voluntary pathways and give rise to characteristic respiratory patterns. The prognosis depends on the level and extent of the lesion.

Adult↗
PubMed1997

Xenopus Pax-6 and retinal development.

We have cloned a homolog of Pax-6 in Xenopus laevis. Its deduced amino acid sequence has a 95% overall identity with Pax-6 homologs in other vertebrates. It is expressed early in development in cells fated to form the eye and parts of the forebrain, hindbrain, and spinal cord. It has two phases of expression in the eye. In the early phase, from stage 12.5 to stage 33/34, Xenopus Pax-6 is expressed throughout the developing retina. In the late phase, after stage 33/34, it is excluded from mature cells in the outer half of the retina and from cells in the ciliary marginal zone, remaining only in amacrine and ganglion cells. Misexpression of Pax-6 early in development results in axial defects, but no specific eye phenotype is observed. Targeted misexpression in the retina at later stages does not result in any significant bias toward formation of amacrine or ganglion cells or away from photoreceptors. Ectopic expression of the proneural gene NeuroD alters the pattern of Pax-6, substantially reducing its expression in the eye field and later reducing or eliminating the eye itself. Our results show that Pax-6 expression appears to be necessary, but not sufficient, for eye formation in Xenopus.

Amino Acid Sequence↗
PubMed1997

Xenopus Brn-3.0, a POU-domain gene expressed in the developing retina and tectum. Not regulated by innervation.

PURPOSE: To study the effect of denervation on the expression of the POU-domain gene Brn-3.0 in the Xenopus visual system. METHODS: An oligonucleotide probe was used to identify homologs of the murine gene Brn-3.0 in the retina. In situ hybridization was used to determine the spatial distribution of the mRNA within the developing embryo. To study the effects of denervation on Brn-3.0 expression and cell fate, embryonic eyes were transplanted to an ectopic location on the animal (the flank) before the onset of retinal ganglion cell (RGC) axonogenesis. Gene expression in ectopic eyes and denervated tecta was analyzed over time using in situ hybridization. RESULTS: The deduced, partial amino acid sequence for Xenopus Brn-3.0 shows 100% identity with the mouse Brn-3.0 and the human Brn-3a gene products. It is expressed during early embryonic development in distinct populations of the neural crest and later in specific cranial ganglia. It also is expressed in RGCs and in the optic tectum, beginning before the first RGC axons have reached the tectum and continuing without interruption throughout the period when retino-tectal connections are established and refined. If the retino-tectal projection is kept from forming by transplanting one eye to an ectopic location, Brn-3.0 expression is unaffected in both the ectopic eye and the denervated side of the tectum. CONCLUSIONS: Coordinate expression of Brn-3.0 in afferent and efferent pathways suggests mutual regulation. However, the authors' evidence shows that expression in the retina is not regulated by target-derived factors nor is expression in the tectum regulated by retinal innervation.

Animals↗
PubMed1996

Distinguishing cerebrospinal fluid from saline used to identify the extradural space.

Because of the potential seriousness of unrecognized dural puncture during the performance of extradural analgesia and the widespread use of normal saline for the "loss of resistance" technique, it is important to differentiate between cerebrospinal fluid (CSF) and saline dripping from the extradural needle. During insertion of lumbar drains in 10 neurosurgical patients, we first identified the extradural space using saline for loss of resistance. Temperature (using the back of the gloved hand), pH, glucose and protein (using urine testing sticks) were tested by a blinded observer for ability to distinguish saline aspirated from the extradural space from CSF aspirated on establishing the dural puncture. Temperature, glucose and protein were independently 100% accurate in distinguishing saline from CSF. One saline sample had a pH value greater than 7 compared with nine CSF samples. We conclude that simple bedside testing for temperature, glucose, protein and pH accurately distinguished between CSF and saline used to identify the extradural space.

Adult↗
PubMed1995

The evolution of heart, lung and liver transplantation services in Australia.

The introduction and operation of heart, lung and liver transplantation services in Australia have been assisted by a Nationally Funded Centres policy adopted by health ministers. Assessment for eligibility for support under the program has been undertaken by the Australian Health Technology Advisory Committee. Outcomes/survival rates at transplantation centres have compared favourably with results from other countries. As in other countries, shortage of donor organs has limited the number of procedures undertaken. Some concern remains regarding the viability of newer transplantation programs which are now being established in smaller centres of population.

Australia↗
PubMed1995

The evolution of laparoscopic surgery in routine health care.

While laparoscopic cholecystectomy is now widely used, diffusion of other laparoscopic surgical methods has been more modest. Uptake of most laparoscopic methods has been influenced by considerations of effectiveness compared with open surgery, competing minimally invasive therapies, and the inconvenience and cost of technical change.

Australia↗
PubMed1995

Comparison of direct blood pressure measurement at the radial and dorsalis pedis arteries during surgery in the horizontal and reverse Trendelenburg positions.

The differences in simultaneous arterial pressure measurements from the radial and dorsalis pedis arteries were studied in anaesthetised adult patients in either the horizontal or reverse Trendelenburg position. Significantly higher pressures were measured from the dorsalis pedis artery than from the radial artery in both positions, even allowing for the hydrostatic effect on the dorsalis pedis arterial pressure in the non-horizontal group. If the dorsalis pedis artery is to be used to measure direct arterial blood pressure, we recommend that readings be compared with an arm sphygmomanometer to avoid potentially dangerous hypotension being missed.

Adult↗
PubMed1995

The status of laparoscopic surgery in Australia.

Laparoscopic surgery continues to evolve and to offer major potential for achieving benefits to patients and to health care providers because of decreased morbidity. Laparoscopic cholecystectomy has diffused rapidly and widely. However, the spread of other minimal access surgery methods has been more gradual, reflecting uncertainties as to the degree of benefit and rate of change of technology. Firm evidence of efficacy and costs of the new methods is still limited, and a number of organisational issues continue to demand attention.

Australia↗
PubMed1995

Acute and chronic effects of winter swimming on LH, FSH, prolactin, growth hormone, TSH, cortisol, serum glucose and insulin.

The present investigation is based on a 2.5 months selbstversuch (self-experiment) of the authors, between October 21 1992, and January 6 1993. 11 healthy students, five females and six males, age 24 to 29 years, and their teachers underwent regular winter swimming at least once a week, for 2 to 10 minutes, at the natural water temperature (6.8 degrees C (October 1992) to 2.0 degrees C (January 1993)) in the southern Baltic Sea. Blood samples were drawn before and 30 and 60 minutes after the cold bath, both at the first and the last day of the swimming season. TSH increased from 0.96 mU/l to 1.42 mU/l (p < 0.01) in the untrained, and from 0.93 mU/l to 1.43 mU/l (p < 0.01) in the cold-trained persons, and decreased thereafter (p < 0.01). Similar changes occurred in cortisol serum concentrations, though psychological stress seemed to interfere with cold stress. Cortisol increased from 99 ng/ml to 133 ng/ml in the untrained, and from 101 ng/ml to 137 ng/ml (p < 0.05) in the cold-trained persons within 30 minutes after cold water immersion, and decreased thereafter (p < 0.01). There were mild decreases in prolactin serum levels after cold stress, whereas FSH, LH and growth hormone remained unaltered. There was a mild initial elevation of serum glucose after cold stress (plus 12 mg/dl, (p < 0.01)) which disappeared after training. There were long term training effects besides the effects on glucose: Basal prolactin levels increased by almost the factor two, and insulin serum levels dropped by almost 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[HLA typing in high risk keratoplasty].

UNLABELLED: Improved microsurgical techniques and better immunosuppressive treatment have led to an increase in the number of corneal transplantations. However, graft rejection due to a disparity between donor and recipient major histocompatibility antigens remains the major complication. The risk of graft rejection is further increased in patients with vascularized graft beds and in presensitized persons. Well-designed experimental studies and clinical experience have clearly shown the importance of class-I-antigens. However, class-II antigens have not yet been studied to the same extent. METHODS: Multiorgan donors and corneal graft recipients were HLA typed using the lymphocytotoxicity test previously described by Terasaki. The recipients were typed retrospectively. Cadaver corneal graft donors were typed using a novel HLA typing technique on retinal pigment epithelial cells, as previously described by us. Postoperatively, all recipients were routinely examined for rejection over a period of 2 years. RESULTS: Graft rejection was observed in 25% of the 133 high-risk patients. Of the 13 class-I-typed patients who showed a rejection 9 persons had two or more major histocompatibility mismatches. Of the 12 patients without rejection problems only 5 had two or more HLA class-I-mismatches. Of the patients with one or two matches at the HLA-DR locus there were only 4 out of 9 patients with at least one graft rejection; 5 out of 6 patients showed no signs of rejection. CONCLUSIONS: Mismatches at either class-I- or class-II- gene loci lead to a higher frequency in corneal graft rejection. Apart from the major histocompatibility mismatches, other factors also influence graft rejection, such as the distance between the corneal transplant and corneal vessels, presensitization, and the indication for corneal grafting. If we are to define the factors influencing graft rejection better and further increase our knowledge on the role the major histocompatibility antigens play in corneal graft rejection in a larger patient group, then cooperation with other transplantation centers will be required.

Graft Rejection↗
PubMed1992

Pipecuronium versus high dose vecuronium. II. A comparison of speed of onset and cumulation during propofol anaesthesia.

The onset time and tendency to cumulation of pipecuronium and high-dose vecuronium were compared during nitrous oxide anaesthesia supplemented with a propofol infusion. Pipecuronium 0.06 mg.kg-1 had a similar duration of action to vecuronium 0.2 mg.kg-1 (49 vs 43). Patients who received vecuronium had a shorter onset time of neuromuscular blockade (p less than 0.01). Neither pipecuronium nor vecuronium showed marked cumulation.

Adult↗
PubMed1991

Effect of arterial carbon dioxide tension on the duration of action of atracurium.

The duration of action of atracurium was studied in two groups of patients. In group I (n = 15), patients' lungs were hyperventilated to a mean PaCO2 of 3.3 kPa and in group II (n = 15) lungs were ventilated to maintain a mean PaCO2 of 5.3 kPa. Anaesthesia was maintained using an infusion of propofol. The time taken to return to a T1 twitch height of 10% of control was measured following each incremental dose of atracurium 0.15 mg kg-1. It was found that the duration of action of atracurium was significantly (P less than 0.0005) shorter in the hypocapnic group.

Adolescent↗