Developmental transitions in the myosin heavy chain phenotype of human respiratory muscle

The renal lymphatic system plays an important role in removing excess fluid from the kidneys. Unfortunately, the factors influencing lymphatic flow are difficult to measure. We used a simple model to represent renal lymphatics as a single pressure source (PL) pushing lymph through a single resistance (RL). In anesthetized dogs, we cannulated renal lymphatics and measured lymph flow rate (QL) as we varied pressure (PO) at the outflow end of the lymphatics. There was no significant change in QL as we increased PO from -5 to 0 cm H2O. In other words, there was a plateau in the QL vs. PO relationship. At higher PO's, QL decreased linearly with increases in PO. From this linear relationship, we calculated RL as -delta PO/ delta QL and we took PL as the PO at which QL = 0 microliter/min. At baseline, RL = 0.34 +/- 0.14 (SD) cm H2O.min/microliter and PL = 8.2 +/- 4.4 cm H2O. When we increased renal venous pressure (PV) from baseline (3.5 +/- 3.0 cm H2O), the plateau in the QL vs. PO relationship extended to higher PO's, RL decreased, and PL increased. Renal interstitial fluid volume and interstitial pressure increased following elevation of PV. The extension of the QL vs. PO plateau with increasing PV suggests that renal interstitial pressure may partially collapse intrarenal collecting lymphatics which may compromise lymph flow.     

Effects of bilateral lesions of auditory cortex in mice on the acoustic startle response

The acoustic startle response (ASR) was used to investigate the effects of auditory cortical lesions on a brain stem-mediated auditory behavior. The ASRs were obtained longitudinally from young adult C57BL/6J mice before bilateral ablation of auditory cortex, 1 day after ablation, and 1 month later. Control mice received lesions of nonauditory cortex. For some mice, averaged brain stem-evoked responses (ABR) were obtained, and these indicated no effects of lesions on auditory sensitivity. One month after surgery, mice with auditory cortex ablations were statistically indistinguishable from controls on all suprathreshold measures of ASR. However, 1 day after ablation of auditory cortex, experimental animals (but not controls) exhibited a change in ASR amplitude (but not threshold or latency). When a noise burst of 80 dB SPL was used to elicit the ASR, the amplitude was diminished, but with a 110 dB stimulus, amplitude was enhanced. The findings can be interpreted in one of two ways: temporary interference with modulation of the ASR normally performed by auditory cortex; or a general effect of auditory cortex ablation on brain stem auditory circuits not specific to the ASR. In any event, if auditory cortex plays a modulatory role with regard to the ASR, it is apparently nonessential and/or readily compensated for after ablation.     

Inhibition by propofol (2,6 di-isopropylphenol) of the N-methyl-D-aspartate subtype of glutamate receptor in cultured hippocampal neurones

1. The effects of propofol (2,6 di-isopropylphenol) on responses to the selective glutamate receptor agonists, N-methyl-D-aspartate (NMDA) and kainate, were investigated in cultured hippocampal neurones of the mouse. Whole cell and single channel currents were recorded by patch-clamp techniques. Drugs were applied with a multi-barrel perfusion system. 2. Propofol produced a reversible, dose-dependent inhibition of whole cell currents activated by NMDA. The concentration of propofol which induced 50% of the maximal inhibition (IC50) was approximately 160 microM. The maximal inhibition was incomplete leaving a residual current of about 33% of the control response. This inhibitory action of propofol was neither voltage- nor use-dependent. 3. Analysis of the dose-response relation for whole cell NMDA-activated currents indicated that propofol caused no significant change in the apparent affinity of the receptor for NMDA. 4. Outside-out patch recordings of single channel currents evoked by NMDA (10 microM) revealed that propofol (100 microM) reversibly decreased the probability of channel opening but did not influence the average duration of channel opening or single channel conductance. 5. Whole-cell currents evoked by kainate (50 microM) were insensitive to propofol (1 microM-1 mM). 6. These results indicate that propofol inhibits the NMDA subtype of glutamate receptor, possibly through an allosteric modulation of channel gating rather than by blocking the open channel. Depression of NMDA-mediated excitatory neurotransmission may contribute to the anaesthetic, amnesic and anti-convulsant properties of propofol.     

Hypothyroidism and hyperthyroidism in major depression revisited

BACKGROUND: The aim of our study was to evaluate the prevalence of thyroid abnormalities among depressed outpatients and to examine the response to treatment of those subjects with relatively low or high thyroid hormone levels. METHOD: Outpatients (N = 200) 18 to 65 years of age who met DSM-III-R criteria for major depression were screened for the presence of thyroid abnormalities using a number of thyroid indices. Of these patients, 166 were then treated openly with the antidepressant fluoxetine for 12 weeks. We assessed whether patients with relatively low or high thyroid hormone levels had a different response to treatment compared with other patients. The 17-item Hamilton Rating Scale for Depression (HAM-D-17) was administered during the study to assess changes in depressive symptoms. Thyroid function was assessed by measuring T3, T4, free T4 index (FT4I), T3 uptake (T3U), and serum thyroid-stimulating hormone (TSH) levels. RESULTS: No clinical cases of hyperthyroidism or hypothyroidism were detected. Of the patients examined, 5 (2.6%) had slightly elevated TSH levels (range, 4.7-8.2); none of these had T4 or FT4I levels below the normal range. Subnormal levels of T4 or FT4I were found in 1 subject (0.5%). T3 and T3U levels were below the normal range in a larger number of patients (7.6% and 15.0% respectively), but only 1 of these patients had elevated TSH levels. None of the patients had levels of TSH below the normal range, and only 3 subjects (1.5%) had T4 levels above the normal range. No relationship was found between response rate (assessed as either change in HAM-D-17 score or as remission of depressive symptoms with a HAM-D-17 score < or = 7 for 3 consecutive weeks) and each of the thyroid tests, even after adjusting for baseline severity of depression. CONCLUSION: In depressed outpatients, it appears that hypothyroidism and hyperthyroidism are extremely uncommon and that the presence of subtle thyroid function abnormalities does not have an impact on treatment outcome.     

Polarisation-dependent optical gain in ridge-waveguide laser diodes

The polarisation dependence of the optical gain in quasi-index-guided, lambda =1.3 mu m, GaInAsP-InP, metal-clad, ridge-waveguide laser diodes is demonstrated. It is shown experimentally that, depending on the lateral waveguiding, either the TE or the TM-polarised mode is favoured. By appropriate design of the laser structure, almost polarisation-independent internal optical gain has been experimentally achieved.<>     

Primary oral squamous cell carcinoma: a review of 92 cases

PURPOSE: This is a retrospective review of 92 cases of oral squamous cell carcinoma treated by one department of oral and maxillofacial surgery. PATIENTS AND METHODS: The medical records of 92 patients with oral squamous cell carcinoma were reviewed, and standard epidemiologic data were obtained. In addition, cases were identified as to site, stage, risk behavior, histologic classification, primary and secondary surgical treatment, adjunctive therapy, and survival rates. RESULTS: The results indicate a higher-than-predicted 2-year survival rate. The association between alcohol and tobacco consumption and incidence of disease is supported. There was a correlation between tumor size and survival rate, but no correlation between histologic classification and prognosis. CONCLUSION: Mortality increases in relation to the stage at which the diagnosis of oral squamous cell carcinoma is made. Patients with stage III or IV lesions have a much poorer prognosis than those with stage I or II lesions. However, histologic classification and prognosis were not correlated.